Of course the insect visitors - bees and flies chiefly - alight on the showy staminate blossoms first, and transfer pollen from them to the dull pistillate ones later, as it was intended they should, to prevent self-fertilization.How endless are the devices of the flowers to guard against this evil and to compel insects to cross-pollinate them! The most minute detail of the mechanism involved, which the microscope reveals, only increases our interest and wonder.
Any plant which elects to grow in shallow water must be amphibious; it must be able to breathe beneath the surface as the fish do, and also be adapted to thrive without those parts that correspond to gills; for ponds and streams have an unpleasant way of drying up in summer, leaving it stranded on the shore.This accounts in part for the variable leaves on the arrowhead, those underneath the water being long and ribbon-like, to bring the greatest possible area into contact with the air with which the water is charged.Broad leaves would be torn to shreds by the current through which grass-like blades glide harmlessly; but when this plant grows on shore, having no longer use for its lower ribbons, it loses them, and expands only broad arrow-shaped surfaces to the sunny air, leaves to be supplied with carbonic acid to assimilate, and sunshine to turn off the oxygen and store up the carbon into their system.
WATER ARUM; MARSH CALLA
(Calla palustris) Arum family Flowers - Minute, greenish yellow, clustered on a cylinder-like, fleshy spadix about 1 in.long, partly enfolded by a large, white, oval, pointed, erect spathe, the whole resembling a small calla lily open in front.The solitary "flower" on a scape as long as the petioles of leaves, and, like them, sheathed at base.
Leaves: Thick, somewhat heart-shaped, their spreading or erect petioles 4 to 8 in.long.Fruit: Red berries clustered in a head.
Preferred Habitat - Cool Northern bogs; in or beside sluggish water.
Flowering Season - May-June.
Distribution - Nova Scotia southward to Virginia, westward to Minnesota and Iowa.
At a glance one knows this beautiful denizen of Northern bogs and ditches to be a poor relation of the stately Ethiopian calla lily of our greenhouses.Where the arum grows in rich, cool retreats, it is apt to be abundant, its slender rootstocks running hither and thither through the yielding soil with thrifty rapidity until the place is carpeted with its handsome dark leaves, from which the pure white "flowers" arise; and yet many flower lovers well up in field practice know it not.Thoreau, for example, was no longer young when he first saw, or, rather, noticed it."Having found this in one place," he wrote, "I now find it in another.
Many an object is not seen, though it falls within the range of our visual ray, because it does not come within the range of our intellectual ray.So, in the largest sense, we find only the world we look for."Now, the true flowers of the arum and all its spadix-bearing kin are so minute that one scarcely notices them where they are clustered on the club-shaped column in the center of the apparent "flower." The beautiful white banner of the marsh calla, or the green and maroon striped pulpit from which Jack preaches, is no more the flower proper than the papery sheath below the daffodil is the daffodil.In the arum the white advertisement flaunted before flying insects is not even essential to the florets'
existence, except as it helps them attract their pollen-carrying friends.Almost all waterside plants, it will be noticed, depend chiefly upon flies and midges, and these lack aesthetic taste.
"Such plants have usually acquired small and inconspicuous separate flowers," says Grant Allen; "and then, to make up for their loss in attractiveness, like cheap sweetmeats, they have very largely increased their numbers.Or, to put the matter more simply and physically, in waterside situations those plants succeed best which have a relatively large number of individually small and unnoticeable flowers massed together into large and closely serried bundles.Hence, in such situations, there is a tendency for petals to be suppressed, and for blossoms to grow minute; because the large and bright flowers seldom succeed in attracting big land insects like bees or butterflies, while the small and thick-set ones usually do succeed in attracting a great many little flitting midges." Flies, which are guided far more by their sense of smell than by sight, resort to the petalless, insignificant florets of the ill-scented marsh calla in numbers;and as the uppermost clusters are staminate only, while the lower florets contain stamens and pistil, it follows they must often effect cross-pollination as they crawl over the spadix.But here is no trap to catch the tiny benefactors such as is set by wicked Jack-in-the-pulpit, or the skunk-cabbage, or another cousin, a still more terrible executioner, the cuckoo-pint (Arum maculatum)of Europe.
Few coroner's inquests are held over the dead bodies of our feathered friends; and it is not known whether the innocent-looking marsh calla really poisons the birds on which it depends to carry its bright seeds afar or not.The cuckoo-pint, as is well known, destroys the winged messenger bearing its offspring to plant fresh colonies in a distant bog, because the decayed body of the bird acts as the best possible fertilizer into which the seedling may strike its roots.Most of our noxious weeds, like our vermin, have come to us from Europe; but Heaven deliver us from this cannibalistic pest!