Weeds where woods once were.


“Between forest and field, a threshold
like stepping from a cathedral into the street–
the quality of air alters, an eclipse lifts,
boundlessness opens, earth itself retextured
into weeds where woods once were.”

Ravi Shankar’s poem “Crossings” describes something quite familiar to us all: the edge of the forest.  The speaker is struck by the clear division between a forest and a field, by how different it feels, even, to step from one to the other, from the cathedral-like hush of the forest under the canopy to the wide-open world of a field.  What Shankar is describing here is, in fact, an ecological phenomenon, one called an ecotone.

An ecotone is a transition between two biomes and can be regional (such as between an entire forest and grassland ecosystems) or local (such as the line between a forest and a field).  The name comes from the Greek  words oikos, meaning household or place to live (“ecology” is the study of the place you live!) and tonos, or tension.  So an ecotone is a place where two environments are in tension.

The most interesting part of an ecotone is how it allows for blending of the different organismal communities.  On either side of the boundary, species in competition extend as far as they can before succumbing to other species.  The influence of these two communities on each other is called the edge effect.  Some species actually specialize in ecotonal regions, using this transitional area for foraging, courtship, or nesting.

Terrestrial environments are not the only ones in which we can experience Shankar’s “threshold” between biomes.  There are also land-to-water ecotones, such as marshes or wetlands, and strictly aquatic ecotones, such as estuaries, where a river meets the sea.  Perhaps in these more dramatic transitions it is easier to see how some species can thrive in this unique habitat.

Even without knowing the biology behind ecotones, it is possible to sense the tension inherent in this boundary.  When hiking on a hot summer day, when the trail leads into a forest it’s like an exhalation.  We, as animals, sense the natural world much more acutely than society would like us to believe.  Ravi Shankar, using the skills of the poet to express what the rest of us cannot verbalize, notes this feeling, writing:

Even planes of motion shift from vertical
navigation to horizontal quiescence:
there’s a standing invitation to lie back
as sky’s unpredictable theater proceeds.
Suspended in this ephemeral moment
after leaving a forest, before entering
a field, the nature of reality is revealed.  


“Crossings,” by Ravi Shankar.  Read it here.

“Ecotone.”  Wikipedia.  Link.

Senft, Amanda.  2009.  Species diversity patterns at ecotones.  (Master’s thesis). University of North Carolina.  Link.

Darkness thickens our feathers


One of the greatest dangers to wild birds worldwide is predation by the domestic cat, Felis catus.  This issue has gained more attention recently with the proposed ban on cats in New Zealand.  In response to data that New Zealand cats had succeeded in killing off nine native species and endangering 33, economist and environmentalist Gareth Morgan suggested that cats should eventually be eliminated from his country.  New Zealand isn’t the only country with a problem, however: in a study of cat predation in the United States, kill rates were found to be two to four times higher than previously thought, with a median estimate of 2.4 billion birds killed each year.

Caleb Parkin’s poem “The Angry Birds,” addresses the threat of the housecat and the willful ignorance of its human owners.  Written from the point of view of a bird observing a hunting cat, a sense of dark foreboding hangs over each word:

Dusk.  The swish of the tear
in the door.  Silence.  The sky a cage
of black-blue branches.  Breathing.
A darkness thickens our feathers,
sticks to the points of our beaks.  
We petrify.  By the table of bait, 
it waits.  A first screech flickers
life into the street-lights.  Then–
reflected on narrow green eyes–
a manicured lawn of limbs.
The baby ape takes in tiger cubs.  
We watch you through the glass,
face alight, twiddling your thumbs.
Playing games in the night,
with our heads.
From up here, we look down on
the pastel television-picture within:
Kitty returns, is named, tickled under the chin:
delicately purrs at an opening tin.
And you, unwitting napkin,
with blood all over
your hunter’s hands.

In this poem, the human is “the baby ape” who has taken in “tiger cubs.”  This language emphasizes the ferocity of the cat, and the human’s position as unwitting ally.

The numbers involved from the previously-mentioned study suggest that cats are very likely causing population declines in some species of birds.  So why are we surprised that so many birds are being killed?  Most likely, this is because cat owners only see a small fraction of their cat’s prey.  A recent study by the University of Georgia with National Geographic obtained estimates of domestic cat predation by attaching video cameras to cats in order to investigate the cats’ activities.  They found that 44% of the cats they studied killed wildlife.  Of these predators, only 23% brought captured prey home, while 49%  left prey at the site of capture, and 28% consumed what they caught.  These results support that previous studies (and owners!) have been significantly underestimating the effect of cats on native wildlife.

So if even well-fed domestic cats are indicated in the decline of local bird populations, what’s a cat owner to do?  Obviously, keeping a cat indoors is the best solution to the problem.  If, for whatever reason, you need to allow your cat outdoor access, there are still steps to curb bird predation.  Never praise a cat that has caught a bird, since positive reinforcement will only enhance this behavior.  Keeping claws trimmed will hinder a cat trying to climb trees or catch wild birds, and a bell on the cat’s collar may warn birds of its approach.  Finally, never feed feral or stray cats.  The instinct to hunt is independent of hunger, and, simply, a well-fed cat has more energy to catch birds.  Report stray cats to a no-kill shelter or humane society.  Remember that, technically, cats are an invasive species, and it is within our grasp to control their effect on the environment.


Angier, Natalie.  2013.  “That Cuddly Kitty is Deadlier Than You Think.”  New York Times.  Link.

“The Angry Birds.”  by Caleb Parkin.  Read it here.

Loyd et al.  2013.  Quantifying free-roaming domestic cat predation using animal-borne video cameras.  Biological conservation 160: 183-189.  Link.

Morelle, Rebecca.  2013.  “Cats Killing Billions of Animals in the US.”  BBC News.  Link.

Mullany, Gerry.  2013.  “A Plan to Save New Zealand’s birds: Get Rid of Cats.”  International Herald Tribune.  Link.


Special thanks to Caleb Parkin for permission to use his work.  Please check out his blog, Skylab Stories, for weekly science poems, as well as various other creative writings.

Alive beyond compare.


“…the heart, exposed exactly for what it is: homelier
than we’d like to imagine.  And alive beyond compare.  
Here, the heart is the heart, and isn’t
a fist or a flower or a smooth-running engine
and especially not one of those ragged valentines
someone’s cut out, initialed, shot full of cartoon arrows:
the adolescent voodoo of desire.  Here, nothing’s colored
that impossibly red.”  

In honor of the holiday, I’d like to consider the human heart.  No, not the one usually found in poetry, but the one actually inside of you; the one functioning to carry blood throughout your body, the one transporting oxygen and nutrients and chemicals to every extremity.  David Clewell’s poem “Not to Mention Love: A Heart for Patricia,” is, as the title implies, a love poem written (almost) without the word “love”.  Clewell has tried to

“keep the heart in its proper place for once.  It’s not
in my mouth or on my sleeve  or winging its way lightheartedly 
in circles over my head.  It’s more or less right
where it belongs inside of me, no small thing.”  

So, dispensing with hyperbole and flowery romantic language, what we have left is the heart itself.  Put most simply, the heart is just a muscular pump.  But what is its function?  And how does it work?

Inside your heart are four chambers (fun fact: while mammals have four chambers, reptiles and amphibians have three, and fishes, without the need to breathe air, have only two).  The top two are the left atrium and right atrium (plural: atria), and the lower two are the left and right ventricles.  (The “left” and “right” designation always refers to the animal/person whose heart it is: so if a surgeon was looking down a patient, the left ventricle would be on the patient’s left).  Each chamber bears a one-way valve so that when the chamber is contracting, blood can come in, but when the muscles relax, the valve is shut.

The heart works with a two-stage contraction (the contraction phase is called “systole”).  In the first stage, the right and left atria contract simultaneously, pumping blood through their associated valves into the right and left ventricles.  In the second stage of contraction, the right and left ventricles contract simultaneously to push blood out of the heart.  This two-stage process is why you hear a heartbeat as two sounds “lub-DUB”–that’s the sound of your heart valves closing.  After the contraction, the heart muscle relaxes, a phase called “diastole.”  As Clewell writes,

“There’s nothing cute about it.  The heart 
is the heart, chamber after chamber.  Ventricular.  Uncooked.  
In all its sanguine glory.  I couldn’t make up a thing
like that.  The heart’s perfected its daily making do, the sucking
and pumping, its mindless work: sustaining a blood supply
that’s got to go around a lifetime.”  

(This last point is not exactly true.  Blood is, in fact, produced in the bone marrow).  In their contractions, the right and left sides of the heart fulfill different functions.  Blood returning from the body is oxygen-poor and enters the right side of the heart (atrium to ventricle).  The right ventricle sends this blood out to the lungs to be oxygenated (and to release carbon dioxide).  This blood then returns to the left side of the heart (atrium to ventricle again) where the much-larger left ventricle pumps oxygenated blood out to the entire body.

But it’s Valentine’s Day!  What about love?

What we call “love” is a combination of emotional attachment and brain chemicals.  Though we may seem to feel things in our “heart”, the heart really has only one thing to do with love: it acts to circulate the aforementioned brain chemicals (dopamine, serotonin, and oxytocin) in the blood out to the body and all the rest of the organs, where they can have the physiological effects that make us feel love.  Does this mean love is all in our heads?  Not at all.  It’s everywhere inside of us, thanks to our powerful hearts.

“Sure, there’s a brain somewhere, another planet,
just seconds or light-years away, and maybe some far-flung
intelligence madly signalling for all it’s worth–
but the heart wouldn’t know about that.  It has its own
evidence to go on.  What’s convincing to the heart
is only the heart.  It doesn’t have the luxury of stopping
to weigh, to reconsider, to fold and unfold the raw data of the world
until it’s creased beyond recognition.  Some days it can’t distinguish 
a single sad note from a chorus of exhilaration, but still
the heart has its one answer down to a science: yes.  Over
and over, the iambic uh-huh.  Whatever it takes, some kind of nerve
or unlikely grace: the heart never knows what to think.”


Bianco, Carl.  1999.  “How Your Heart Works.”  HowStuffWorks.com.  Link.

“Biological basis of love,” Wikipedia.  Link.

Boston Scientific.  2009.  “Heart Valves.”  Link.  (Check out the cool animations on this site as well!)

“Not to Mention Love: A Heart for Patricia,” by David Clewell.  Read it here.

Wilson, Sue.  2002.  “Red Gold: the Epic Story of Blood.”  pbs.org.  Link.

The dead float back toward them.

Sockeye salmon photo by Phillip Colla. www.oceanlight.com

Sockeye salmon photo by Phillip Colla. http://www.oceanlight.com

Kim Addonizio is probably my favorite contemporary poet.  She can infuse such sadness, such wistful longing into her works, with a talent for such human description that is never too overwhelmingly emotional.  In her poem “Salmon,” she describes the experience of seeing adult salmon at the end of their long journey, laying eggs and then dying:

In this shallow creek
they flop back and forth and writhe forward as the dead
float back toward them.  Oh, I know
what I should say: fierce burning in the body
as her eggs burst free, milky cloud
of sperm as he quickens them.  I should stand
on the bridge with my camera,
frame the white froth of rapids where one
arcs up for an instant in its final grace.”  

The life of a salmon is unique among fish.  All Pacific salmon species are anadromous, which means that they are born in freshwater and spend their adult lives in saltwater, returning to breed in natal rivers.  After a 2-3 month incubation period, eggs in freshwater hatch into what are called alevin.  The alevin are still connected to the yolk sac, and continue to feed on it for the first few months while the mouth and digestive system develop.  See below for a great image of a freshly hatched alevin, complete with vascularized yolk sac:


Once the alevin consumes the yolk sac, it is called a fry.  Fry emerge from the gravel nest in the stream bed in order to feed (some species take off for the ocean at this point; others remain in freshwater for a longer period of time).  The salmon fry will begin to develop vertical stripes, at which point it is called a parr.  The vertical stripes are thought to act as camouflage, allowing the parr to blend in among the rocks and stream  vegetation.  Again, depending on species, the salmon parr stay in freshwater from six months to three years, feeding and growing larger in preparation for the journey out to sea.  When it is time, the parr lose their markings and turn a silvery color, at which point they are called smolts.  Smolts begin to school in large groups and gradually allow their bodies to become accustomed to salt water, often spending time in brackish water before finally achieving the ocean.  After a few years, the smolts have become adult salmon, and live entirely in a saltwater environment for 1-5 years.

One thing that I find incredibly interesting about the salmon is its anadromous lifestyle; the ability to move from freshwater to saltwater and then back without major trauma.  From a biology standpoint, this ability is simply amazing.  Saltwater contains about 1000 times more ions than freshwater (salt, sodium chloride, is broken down into its most stable form in water: sodium ions and chloride ions).  This is a problem for an animal living in either environment.  The internal environment of a fish, for instance, is optimized to be at an intermediate salinity.  The fish must have what is called an osmoregulatory system in order to maintain the balance of water and ion in its aquatic environment.

So, in freshwater, the fish is in an environment where its body is ‘saltier’ (contains more ions) than its surroundings.  To deal with it, its kidneys work to dump water; in other words, it urinates frequently.  At the same time, the fish takes in ions (there are a few, even in freshwater!) through its gills.

In saltwater, on the other hand, it is the opposite.  The surrounding water is much saltier (more ions!) than its body, and has the effect of being dehydrating to the fish.  To deal with this, a fish drinks a lot of water, but does not urinate.  Salt is stripped away from the water it drinks and is secreted by the gills.

Possessing the capacity to osmoregulate in either environment is a physiological miracle in itself.  Being anadromous means that a salmon can actually switch from one mode to another and back.  The first transition, from fresh to saltwater, is arguably the most incredible since during this period the smolts actually restructure their entire physiology prior to changing environments.

The return journey, back to freshwater, is no less amazing than the journey out.  Salmon return to the same rivers they hatched in to spawn.  A salmon is considered mature when it begins to change to a deeper color.  Male salmon prepare for combat by developing other striking features: a distinct hump, canine teeth, and a kype, or pronounced curvature of the jaws.  These mature salmon spend anywhere from a day to a week at the mouth of the river  and then begin to travel upriver, using the same route taken as a smolt.  This homing ability is thought to be facilitated in large part by the salmon’s sense of smell; they can actually smell where they were born and navigate towards it.

Salmon can travel hundreds of miles upstream to reach a spawning ground.  Very few survive the journey, and those that do manage to lay or fertilize eggs are beset by accelerated aging.  Their bodies begin to rapidly deteriorate right after spawning as a result of the release of massive amounts of corticosteroid hormones.  It is at this point that Addonizio observes the salmon, having fought hundreds of miles upstream to lay eggs and pass on their genes to the next generation, their bodies wasted and spent, rotting in the sunshine.  She refuses to shy away from this aspect of their lives, writing,

“I have to study the small holes
gouged into their skin, their useless gills, 
their gowns of black flies.  I can’t
make them sing.  I want to,
but all they do is open
their mouths a little wider
so the water pours in
until I feel like I’m drowning.  
On the bridge the tour bus waits
and someone waves, and calls down
it’s time, and the current keeps lifting
dirt from the bottom to cover the eggs.”


“About Pacific Salmon.” Pacific Salmon Commission.  Link.

“Salmon,” by Kim Addonizio.  Read it here.

“Salmon Biology”.  2010.  Salmon Fishing Now.  Link.

“Salmon”.  Wikipedia.  Link.


Jon Velotta was instrumental in writing an understandable explanation of osmoregulation.  Please go check out his research on osmoregulation in the alewife (a river herring).  His webpage is here.

Its bark papyrus, its scars calligraphy

Paper Birch in Fall  53269

As a recent resident of New England, I am still thrilled when I see a stand of birches in the forest.  I love this tree for both its beauty and its usefulness: when camping, there’s no better firestarter in wet weather than the oily paper bark of a downed birch.  But why is this tree so different from other trees?  Why is its bark not fire-resistant, its lack of color so shockingly bright against multitudes of drab trunks?  Why has it inspired so much poetry?

“Is it agony that has bleached them to such beauty?  Their stand
is at the edge of our property–white spires like fingers, through which
the deer emerge with all the tentative grace of memory.”

– Nathaniel Bellows

That pale bark is arguably the distinguishing characteristic of a birch.  To understand why it is different, we must first think about the bark of other trees.

In the most generalized sense, bark is the outer covering of woody plants, encompassing everything outside of the vascular cambium.  There are several layers that make up “bark,” which are (moving from the cambium outward): the phloem, cortex, phelloderm, cork cambium (phellogen), and cork (phellem).  In most trees, bark serves as protection against loss of water by evaporation, attacks by insects, drastic temperature changes, and disease.  In some trees, it even acts as protection against fire damage.  Except for the last, all of these functions are served by the fine, papery bark of a birch.  What makes the birch unique is what its bark contains that other trees do not.

“After a storm, one birch fell in the field, an ivory buttress collapsed across
the pasture.  Up close, there is pink skin beneath the paper, green lichen
ascending in settlements of scales.  In the dark yard it beckons you back”
-Nathaniel Bellows

The chemistry of birch bark is what conveys its most amazing properties, and most likely is what secured this tree’s place in folklore, mythology, and poetry.  Birch bark is white because of the presence of a phytochemical, called betulin.  The total content of betulin ranges from 15-25%, depending on the species.  Betulin is hydrophobic, meaning that it resists water.  The whiteness (protection against light damage) and the water resistance led to birch bark being used in construction of canoes by native Americans.  Both betulin and its derivative, betulinic acid, are being studied for medicinal uses against melanoma, herpes, and HIV.

“The trunks of tall birches
Revealing the rib cage of a whale
Stranded by a still stream”
-William Jay Smith

Throughout history, humans have found a way to use nearly all the parts of the birch, so much so that it is often referred to as the “giving tree.”  It has an amazing ability to survive harsh circumstances, and is a first successional tree, quick to repopulate areas that have succumbed to fire or clear cutting.  (Though I couldn’t find data on this, I wonder if this ability is the reason its bark is not fireproof: fire is actually advantageous to a birch because it eliminates competitors and allows a chance to recolonize).  Because of its abilities, the birch has acquired quite a bit of symbolism in different cultures.  In Celtic cultures, the birch represents growth, renewal, stability, initiation, and adaptability.  In Gaelic folklore, it is associated with the land of the dead, and appears often in Scottish, English, and Irish folklore in association with fairies, death, or returning from the grave.  A tree with such near-legendary qualities and capacity for survival–how could it fail to inspire wonder?

“its bark
papyrus, its scars calligraphy, 
a ghost story written on
winding sheets, the trunk bowing, dead is
my father, the birch reading the news
of the day aloud as if we hadn’t
heard it, the root moss lit gas,
like the veins on your ink-stained hand–
the birch all elbows, taking us in.
-Cynthia Zarin


“Birch,” by Cynthia Zarin.  Read it here.

“Birch,” Wikipedia.  Link.

Krasutsky, Pavel.  2002.  “Birch Bark Extractives.”  University of Minnesota-Duluth.  Link.

“Russian Birch,” by Nathaniel Bellows.  Read it here.

“Winter Morning,” by William Jay Smith.  Read it here.

Ever unreeling


Few creatures inspire so much instinctive fear as the spider.  Perhaps it is the number of legs.  Or the rotund, hairy bodies.  Or the knowledge that some are poisonous to us, without the understanding of which species pose a threat.  Perhaps it is simply the alien nature of their existence: how they can be unseen and everywhere, so different from us, so impossible.

In the first stanza of Walt Whitman’s poem, “A noiseless patient spider,” the author observes the behavior of a spider as it throws out one silken thread after another:

“A noiseless patient spider,
I mark’d where on a little promontory it stood isolated,
Mark’d how to explore the vacant vast surrounding,
It launch’d forth filament, filament, filament out of itself,
Ever unreeling them, ever tirelessly speeding them.”

We’ve all seen a spider dangling inexplicably from the ceiling, or watched it escape on its line of filament.  But how does a spider create silk?  Where does this material come from, and why is it so strong?

As it turns out, spiders have seven different kinds of silk, produced by seven silk glands.  One spider cannot make all seven types of silk; instead, males have at least three different types, and females have at least four.  These glands secrete silk proteins (made of strings of amino acids) dissolved in solution.  Liquid silk is pushed through internal ducts and emerges from microscopic spigots on the spider’s spinnerets (organs at the rear of the spider’s abdomen, designed for just this purpose).  This electron micrograph shows the silk spigots in operation:

Image by MicroAngela

Image by MicroAngela

There is a valve on every spigot that controls the speed and thickness of the silk.  As the spigots exude silk, they pull fibroin protein molecules from the ducts.  With the addition of these protein molecules, the silk becomes stretched out and the molecules link in the air.  The spinnerets wind the strands together to become a silk fiber.  Spider silk is incredibly tough and is stronger by weight than steel.  Some varieties are twice as strong by weight than Kevlar, the toughest man-made polymer.

So what have we done to harness this natural resource?  As early as 1710, a Frenchman, François Xavier Bon de Saint Hilaire, showed Europeans how garments could be made from spider silk.  Recently, an entire golden cape (the natural color of the silk) has been created…with the help of 1.2 million spiders.  Companies have also tried to harness the almost supernatural strength of spider silk, though the problem has always been producing enough in quantity.  A company called Nexia successfully created transgenic goats that could produce spider silk proteins in their milk.  Even that wasn’t enough for mass production, and the company went bankrupt in 2009.  Most recently, in 2012, Dr. Craig Vierra demonstrated techniques to develop and process synthetic spider silk from bacteria.  So the search goes on.

Was Whitman thinking about any of this when he wrote “A noiseless patient spider”?  I doubt it.  But he was, apparently, thinking of how humans are not so different from spiders after all.  Spiders spin their tenuous thread to find their way in “the vacant vast surrounding.”  Whitman recognizes this behavior in his second stanza:

“And you O my soul where you stand,
Surrounded, detached, in measureless oceans of space,
Ceaselessly musing, venturing, throwing, seeking the spheres to connect them,
Till the bridge you will need be form’d, till the ductile anchor hold,
Till the gossamer thread you fling catch somewhere, O my soul.”

In a literal sense, humans build bridges to get from one place to another, planes and cars and buses to carry us there.  But do we not all seek a place?  Do we not seek knowledge and experience and try to understand our surroundings?  Whitman’s soul is doing its best to find a place where he can anchor.  He is casting out his “gossamer thread” and praying it will catch, hoping to be no longer lost in “measureless oceans of space.”  It seems we have much to learn from spiders, perhaps more than we knew.


Harris, Tom. 2002. “How Spiders Work”  HowStuffWorks.com. Link.

Jones, Denna.  2012.  “The gossamer cape: spun by a million spiders.” The Guardian.  Link.

The Journal of Visualized Experiments. “The future of biomaterial manufacturing: Spider silk production from bacteria.” ScienceDaily, 18 Jul. 2012. Link.

“A noiseless patient spider,” by Walt Whitman.  Read it here.

O’Brien, Miles and Marsha Walton.  2010. “Got Silk?”  NSF Science Nation.  Link.

A Wilderness of White

Photograph of a natural snowflake captured with a  specially designed snowflake photomicrograph.  Photo: snowcrystals.com

Photograph of a natural snowflake captured with a specially designed snowflake photomicrograph. Photo: snowcrystals.com

“How full of creative genius is the air in which these are generated!  I should hardly admire more if real stars fell and lodged on my coat.”
 -Henry David Thoreau

In the northeast, winter is a season of cold.  It is a time when outdoor activities are dictated more than ever by the weather.  As children, snow is the stuff of dreams.  It can be mounded, piled, thrown, shaped, dug out, eaten, colored, ridden on, and experienced in a million ways.  As if that isn’t enough, the enduring hope of snow day is ever present, and the moment when you first wake up to that brightness of reflected sunlight through your windows, when you wake up and know it will be a day for only fun, is the lightest feeling in the world.  As adults, snow is polarizing: you love its beauty or hate its inconvenience.  Everyone has heard that every individual snowflake is unique.  But is this true?  And if so, why?

“Out of the bosom of the Air,
Out of the cloud-folds of her garments shaken,
Over the woodlands brown and bare,
Over the harvest-fields forsaken,
Silent, soft, and slow
Descends the snow.”
-Henry Wadsworth Longfellow 

First off: a definition of terms.  Snowflake is a more general term, and can refer to an ice crystal, a single crystal of ice, or to larger clumps of ice crystals that fall in agglomerations.  An ice crystal is not a frozen raindrop.  Liquid water that freezes and falls to the ground becomes sleet.  Rather, ice crystals are formed when water vapor in the clouds condenses directly into ice.  As you may (or may not) remember from chemistry class, ice crystals, each molecule of which is made of an oxygen atom and two hydrogen atoms, form what is called a hexagonal lattice.  The six-sided symmetry of this lattice is what gives snowflakes their six-sided symmetry.  Elaborate patterns emerge as the ice crystals grow in the clouds.

The most basic form of a snow crystal is a hexagonal prism, which includes two basal facets and six prism facets.  Different shapes can occur under different conditions, and the form of a snowflake depends very heavily on temperature and humidity.  The growth of these crystals relies on a balance between branching and faceting.  Branching is due to a property of water molecules and the way they travel through the air: they must diffuse, and thus the surface of a crystal a water molecule reaches first is the one one which it condenses.    A small bump on an otherwise-homogeneous structure is thus more likely to result in a crystalline branch, and once a branch has formed, it is more likely to grow longer.  Facets, on the other hand, are due to the fact that some surfaces of ice crystals grow more slowly than others.  Unlike a bump on a crystal surface, inviting a water molecule to bond, the flat surface of a facet is more likely to remain smooth because there is nothing for the water molecule to attach to.  Therefore, this surface grows more slowly.

Below, see a general guide for the most common forms of snowflakes:

types of snowflakes

For all that we understand about crystalline structure and how ice crystals form, there is even more we don’t know.  Why do the most complex shapes form at high humidity?  Why do the shapes of snowflakes go from plates to columns as the temperature lowers?  Usually, each arm of a snow crystal is different from its other arms.  Air current turbulence causes this: as crystals are blown about, water molecules can condense unevenly as each corner of a snow crystal experiences a different environment in the atmosphere.  So there is truth in the unique design of snowflakes, and it is ultimately due to the randomness of nature, building a snow crystal as it is spun and whipped through the air inside a cloud.  John Hallett, director of the Ice Physics Laboratory in Reno, NV, explains that, “[A snowflake’s] final shape is a history lesson of how the thing grew.  The outside edge of the crystal is where it grew last, and as you go inward you can tell where it was before.”

“Before I melt,
Come, look at me!
This lovely icy filigree!
Of a great forest
In one night
I make a wilderness
Of white”
-Walter de la Mare

The winter has come, and with it, the cold.  Snow has been sparse in this part of the country the last few years, and all we can do is watch and wait.  Will we awake tomorrow morning with the light bright and snow-shattered through our windows, with a kiss of frost on the glass from a storm like those when we were children?  If so, take a minute and think about how these amazing ice creations came to be.  And then go make a snowman.


Griffin, Julia 2011.  The science of snowflakes, and why no two are alike.  PBS Newshour.  Link.

SnowCrystals.com.  Kenneth G. Libbrecht 1999.  Caltech.  Link.

“Snow-Flakes,” by Henry Wadsworth Longfellow.  Read it here.

“Snowflakes,” by Walter de la Mare.

Poisonous moons, pale yellow.


I’ve always had an odd fascination for mushrooms.  It’s something about how ephemeral they are–spotting a bright yellow cap tentatively poking from leaf litter on the forest floor and knowing that I very well could be the only one to ever see this mysterious structure.  Perhaps it’s also the incredible variety of forms: yellow, red, purple, orange, black, glow-in-the-dark, phallic-shaped, round, jelly-like, bearing gills or pores, smelling of dirt and rot and death and how there are always organisms waiting to turn your body back into the earth.

Margaret Atwood’s poem “Mushrooms” reads like it is inspired by the same fascination that I experience.  Read it here.  The language of this poem sings.  It is  an incredibly beautiful description of such an overlooked part of our environment.

“they ooze up through the earth
during the night
like bubbles, like tiny
bright red balloons
filling with water;
a sound below sound…”

Mushrooms are a kind of fungus, and what we typically think of as a “mushroom” is really only one of many possible forms.  A “typical” mushroom, then, consists of several parts.  First, a stalk, or stipe, which rises from the ground, sometimes held within what is called the cup or volva.  If there is a ring around the stipe, that ring is called an annulus.  The stipe terminates in the mushroom cap, also called the pileus.  Under the cap may be pores or gills, which contain the mushroom’s reproductive structures: spores.  White warts on the cap are remnants of the universal veil, a layer of tissue that completely surrounds some species of young mushrooms when they emerge from the ground.

But the mushroom itself is really only the fruiting body of the fungus.  It takes several days for the fungus to create this structure, usually after a good rain, by rapidly pulling in water and inflating preformed cells.  Spores are released within hour or days, and the fruiting body collapses back to the ground.  So if a mushroom isn’t the whole story…what is?

“Underfoot there’s a cloud of rootlets,
shed hairs or a bundle of loose threads
blown slowly through the midsoil.
These are their flowers, these fingers
reaching through the darkness to the sky,”

The actual body of the fungus lies underground.  It is called the mycelium, and is made up of many tiny thread-like filaments, the hyphae.  This is what germinates when a spore settles out on substrate.  In contrast to the fruiting bodies of the fungus, the mycelium can be long-lived and massive.  A species of fungus called Armillaria solidipes  is considered one of the largest and longest-lived organisms: its mycelia covers over 3.4 square miles and it is more than 2,400 years old.

“They feed in shade, on halfleaves
as they return to water,
on slowly melting logs,

Fungi lack chlorophyll, and so do not have the means to produce their own food from sunlight.  Instead, the mycelium feeds either by decomposing organic substances (logs or other dead matter in the soil) or by forming a symbiosis with a living green plant.  Those that break down dead matter are called saprophytic, from the Latin for rotten or dead.  The title of “death-eater” gives mushrooms a dark connotation and infects the imagination with images of this grisly duty.  As Atwood puts it: “flesh into earth into flesh.”  The world, reborn.


North American Mycological Association

Pacioni, Giovanni and Gary Lincoff.  1981.  Simon & Schuster’s Guide to Mushrooms.  Simon & Schuster Inc.  New York, NY.


Nothing Gold


“Nature’s first green is gold/Her hardest hue to hold”

Robert Frost had a way of describing nature that forces the reader to both take notice of the world around them and to think about their own lives, their own experiences.  The poem “Nothing Gold Can Stay” is both a meditation of the changing colors of leaves and of the brevity of beauty.  From the first bright green of a new leaf through the point when “leaf subsides to leaf,” Frost imbues this natural progression with human emotions of loss.  What do these changing colors really mean?

The different colors of leaves are due to three classes of pigments the leaves possess.  Greens are due to chlorophyll pigment, which absorbs light for use in photosynthesis, the process by which plants turn light into usable sugars.  Leaves appear green because these pigments absorb light in most of the color spectrum.  Green is the only color not absorbed, and so that wavelength is transmitted to our eyes.

Yellow, orange and brown colors are due to a class of accessory pigments called carotenoids.  Just like it sounds, these pigments also give color to carrots, as well as bananas, corn, and daffodils.  In leaves, carotenoids work to absorb pigments that chlorophyll can’t, thereby allowing the plant to use more of the sun’s energy.

Finally, the red color of autumn leaves is caused by another accessory pigment, anthocyanin.  In different plants, this pigment can appear red, purple, or blue.  Unlike chlorophyll and carotenoids, anthocyanin does not participate in photosynthesis.  Most anthocyanins are produced in the fall, in response to shortening days and less sunlight.

So the green leaves we see for most of the year actually contain several layered colors, hidden beneath the surface.  Chlorophyll is continuously produced and broken down during the growing season, but as fall approaches, production slows and stops, and finally all the chlorophyll is destroyed.  What we see in many deciduous trees are the remnants: yellows and oranges from the carotenoids that have been there all along, reds from anthocyanins appearing later in the season.  Slowly, the leaves die.

It is difficult to not have a sense of loss as the seasons change around us.  From year to year, after the bright pulse of autumn glory, leaves fall, green disappears, and it feels like an ending.  It is hard to think of the world, reborn, in the spring.  Though perhaps, as Robert Frost wrote, “nothing gold can stay,” we must remember that there will be new beauty in the world, new beginnings.

Think of this, always.


Frost, Robert and Edward Connery Lathem (ed.)  The Poetry of Robert Frost: The Collected Poems.  1969 Reed Business Information, Inc.  http://www.poets.org/viewmedia.php/prmMID/19977

Lee, David and Kevin Gould.  2002.  Why leaves turn red.  American Scientist 90(6): 524.                                        http://www.americanscientist.org/issues/feature/why-leaves-turn-red

“Why Leaves Change” USDA Forest Service. http://www.na.fs.fed.us/fhp/pubs/leaves/leaves.shtm



To me, nature is its own language.  All we can do is struggle to express, in our own feeble way, what the world is trying to give to us.  So much poetry has been written in an attempt to describe the simple color of a leaf in autumn, or the way a spider spins its web, or the unfurling of a fern frond in the early spring–so much written, so little understood.

Science has its own language, complex and focusing on minutiae.  One must undergo years of training to speak this language.  The language of science can exclude, it can isolate, but it can answer the questions of how, of why, of where.  Science can look at nature and ignore the beauty to see the molecules and forces, the pigments and chemicals and selective pressures.

To marry science and language is to attempt to bring the wonder back to the mechanics.  Beauty is everywhere.  It is magical and evanescent, but it can be explained.  Here is my attempt.

“I believe in God, only I spell it Nature” – Frank Lloyd Wright