Page:The New International Encyclopædia 1st ed. v. 07.djvu/857

* FLOWERS AND INSECTS. (61 FLOWERS AND INSECTS. under Bide of the liin the complicated series of muscular efforts and physical strains resulting from the attendance of these insects upon flowers. The perfection of adaptation is attained in the moths and butterflies. These creatures and birds are clearly the most highly and wonderfully spe cialized of all animal-.. The butterfly i- a mo I delicate and elaborate living flying machine, and all its characteristic structures have been drawn out in response to its i le nf life, and of all (he organs, its spiral tongue is the most marvelous in. mechanism and adaptation. Thai the ton (maxilla?) has been evolved in response to the visits to flowers with a deep corolla is. among other facts, suggested by that of its entire ab- sence in many silkworm-moths. These sluggish, short-lived insects do not take liquid food, eo quently by disuse the tongue is either in part or in certain forms entirely atrophied. The steps in development and specialization of the tongue of Lepidoptera, which is adapted for probing either flat or long and tubular corollas, may easily be traced. The end of the tongue is b e- times highly specialized. "Peculiar stiff, sharp- pointed appendages at the end of the lamina' en- able them also to tear open delicate succulent tissues, and make use of the sap in flowers which secrete no honey." In response also to seven impacts and strains, the tip of the tongue of cer- tain moths (Ophideres) are so spiny that they can pierce the skin of plums, peaches, and even oranges. In length, the tongue may vary from a minute pointed rudiment scarcely a millimeter in length to that of the hawkmoths, which may be 80 millimeters long, while in a Madagascar sphinx the tongue is 9'', inches in length, and as there are said to be orchids with flowers as deep as this, there is evidently a relation of cause and effect between the phenomena. Origin of Floral Structures Through In- sect Agency. Having seen that insects have been highly modified in various ways by the use and disuse of organs, while seeking pollen and nectar, we may now inquire into the result of such visits or stimuli upon the flowers them- selves. Many facts and ingenious suggestions have been made by Henslow in his Origin of Floral Structures.' His conclusion is that a flower with a conspicuous corolla or perianth lias originated from "a leaf-bud of which some of the members have already differentiated into carpel- lary, others into stamina] organs, the outer ap- pendages being simply bracts, like, we will say, those surrounding the stamens or ovule of the yew." Insects probably visited the primitive flowers for pollen, but also pierced the juicy tis- sues for moistening the honey. Gradually the nectar was evolved, and after a time the earliest- formed flowers having attracted insects to come to them regularly, a numerous series of dill. tiations would result. The corolla, in all probabil- ity, would be the first to issue out of the tracts. Other changes would follow by degrees and in different combinations. From regular, irregular flowers like those of the pea would arise. But J] uch cha 'I--'. ould be dm I o ai i ii a ol i lie protopla 3m, in eon icqui nee oi irrital ion i ' up by thi tension ''it he in 'I hu», t lu ii. do I i" lieve that thi whole floi world he irisei I rregula r flowei t hat of t he pea, 1 1 . ■ ■. made uch bj thi risit nd ol her rnal influeno When a Qi ei i it tated i.ii. i.i Uj and pri r nearly a an bisect pel led to ■ ■ light upon it on one side only, when approaching it directly from I front, [t then throv all it ight upon t he er oi e of ( he flower, i thi case « it h t he ' ■ tpilioi ceous flowers, with the lips ot labiate eti its weight is sustained by the stamens or style, or i. bot li toget her, as in Epilobium angu tifolii I 'irea-a, Veronica, lark-pur. and mon and never the stamens are ileelinate. a- in horse ehe-innt. Dietamuus. Iv-hium, Amaryllis, I Henslow assumes that the primary cause oi irregu- larity must come from without, from an in — i.e. from the mechanical influence of it- "eight ami pressures. "To this external irritation protoplasm of the eells responds, and givi to tissues which are thrown out to withstand the -train- due to the extranoou- pressures of the in- seet. and so the flower prepare- it-elf to main lain an equilibrium under tin- tensions imposed upon ii. and irregularities are the result." Such modifications occur in the bilobed calyxes of furze and Salvia, with many forms of lips, and in en- larged anterior petals or in dependent stamens, as those of aconite and Epilobium. The lip of l.amium consists of one much enlarged petal, which forms an excellent landing place for a bee to rest upon, while the two lateral petals, not being required, arc atrophied to mere points. lu like manner, the two posterior petals are en- larged to form the hood, presumably due to the backward thrust of the insect's head." In the irregular flowers of the foxglove and the Gloxinia, as well as Petunia to a slight extent, and in the regular campanulate flower-, the tithe of the gamopetalous corolla "has enlarged so a- t.. per mit the ingress of an insect which partly or en- tirely crawls into it: then it i- this tubular part which, more especially having to bear the strain upon it. bulges outward or becomes more or less inflated in form, while the lip or anterior pel ■]. not having to bear the entire burden, is not par ticularly enlarged, if it lie at all." Henslow states that if no more than the lead of an insect eiiier the Mower, "then the corolla shapes itself to fit it": thus the snowherry. Scrophularia. and Epipactis only admit the head- of wasps, which are the regular visitor- of these flowers. How, the deep tuhular corolla of th. evening primrose or the honeysuckle has been brought about is ex- plained by the fact that butterflies, in probing their depth- while on the wing, irritate the tube only, "which thus elongates and contracts, re- sulting in little or no irregularity in the Bowers." Also flowers like the narcissus and evening prim- rose prevent the itiL're-- of Bhi I insects. The origin of irregular Sowers is illustrated by Davernoia adhatodoides, whose curiously shaped lip affords an excellent landing-place for a big bumblebee: "moreover, the two walls slope off. and are gripped by the lees of the bee, so that it evidently can lire an excellent purchase, and thus ritle the flower of its treasure at its ease."