Now what is the object of this frothy pavilion? The life history of the insect, in contrast to that of the cicada, will perhaps throw a little light on that question. In the cicada, as I have shown, the eggs are inserted in the bark, but the young, hatching about six weeks later, immediately forsake the parent tree and enter the ground. But the young of our bittersweet membracis are not thus fickle, the entire life of the insect being spent on the plant. Moreover, its eggs are laid in late summer, and do not hatch until the following spring. What, then, is this canopy of the tree-hopper but the provision of a thoughtful mother, a pavilion about her offspring as a shelter through the winter storms? In early July the tiny hoppers emerge from their egg-cases, and presumably creep out from their luminous domicile, and later on in the season these broods of varying numbers and all sizes are to be seen among the young stems of the plant, their beaks inserted, their pointed heads invariably in the same direction-towards the top of the branch. Even though in flight one of the midgets is seen to alight in violence to the rule, he instantly recognizes his mistake, and quickly glides round to the orthodox position.
This curious insect is chiefly confined to the bittersweet, though he is occasionally found in the company of a much bigger cousin of his on the branches of the locust, where these same telltale corrugated frothy pavilions are often seen to clothe the young twigs in their white tufts, the similar product of the larger species, which thus also presumably spends its entire life upon the locust-tree.
[Illustration]
It is now some thirty years since the scientific world was startled by the publication of that wonderful volume, "The Fertilization of Orchids," by Charles Darwin; for though slightly anticipated by his previous work, "Origin of Species," this volume was the first important presentation of the theory of cross-fertilization in the vegetable kingdom, and is the one that is primarily associated with the subject in the popular mind. The interpretation and elucidation of the mysteries which had so long lain hidden within those strange flowers, whose eccentric forms had always excited the curiosity and awe alike of the botanical fraternity and the casual observer, came almost like a divine revelation to every thoughtful reader of his remarkable pages. Blossoms heretofore considered as mere caprices and grotesques were now shown to be eloquent of deep divine intention, their curious shapes a demonstrated expression of welcome and hospitality to certain insect counterparts upon whom their very perpetuation depended.
Thus primarily identified with the orchid, it was perhaps natural and excusable that popular prejudice should have associated the subject of cross-fertilization with the orchid alone; for it is even to-day apparently a surprise to the average mind that almost any casual wild flower will reveal a floral mechanism often quite as astonishing as those of the orchids described in Darwin's volume. Let us glance, for instance, at the row of stamens below (Fig. 1), selected at random from different flowers, with one exception wild flowers. Almost everybody knows that the function of the stamen is the secretion of pollen. This function, however, has really no reference whatever to the external form of the stamen. Why, then, this remarkable divergence? Here is an anther with its two cells connected lengthwise, and opening at the sides, perhaps balanced at the centre upon the top of its stalk or filament, or laterally attached and continuous with it; here is another opening by pores at the tip, and armed with two or four long horns; here is one with a feathery tail. In another the twin cells are globular and closely associated, while in its neighbor they are widely divergent. Another is club-shaped, and opens on either side by one or more upraised lids; and here is an example with its two very unequal cells separated by a long curved arm or connective, which is hinged at the tip of its filament; and the procession might be continued across two pages with equal variation.
[Illustration: Fig. 1]
