152 FIFTH ANNUAL REPORT 



insects play in the fertilization of plants; and the old idea, that color 

 and perfume in flowers were intended for man's especial pleasure, is 

 giving way to the more natural and philosophic view that they are 

 useful to the plants by attracting the needed insects. 



In Dr. Asa Gray's recent little work, " Hovt" Plants Behave," etc., 

 instances enough are given, in an admirably plain and lucid style, to 

 show the manner in which many flowers are curiously and elaborately 

 constructed so asjusttioi to do of themselves what must necessarily 

 be done for them in order to prevent degeneracy or extinction of the 

 species. Some plants, as Fritz Miiller proved, are so self-impotent that 

 they never produce a single seed by aid of their own pollen, but must 

 be fertilized by that of a distinct species, or even of a supposed dis- 

 tinct genus; while in some cases the pollen and stigma mutually act 

 on each other in a deleterious manner.* The wind [is an important 

 agent in the fertilization of certain plants, and some are fertilized even 

 by the higher animals ; but by far the greater number a^e fertilized, 

 or more strictly speaking, pollenized, by insects ; while the number of 

 species (termed Entomophilce by Delpino) which absolutely depend 

 for pollenation on insect agency is not inconsiderable. These insect 

 pollenizers belong to several Orders, but mostly to the Hymenoptera 

 and Lepidoptera. A familiar example is furnished by our milk-weeds 

 (Ascl&pias), the pollen-masses of which may often be found adhering 

 in pairs to the legs of bees and other insects, and sometimes in such 

 quantities as to prove a real detriment and incumbrance to the bearers. 

 Every year I receive specimens of such pollen-burdened bees, which 

 are generally supposed to be infested with some parasite ; and Mr. 

 James D. Meador, of Independence, lately sent me a very gloomy ac- 

 count of the dangerous condition of his apiary from this cause. Each 

 of the numerous flowers which constitute the well-known umbels is 

 curiously constructed so that the pollen-masses, which look like little 

 flattened, ovoid pieces of wax, can only come in contact with the 

 stigma by artificial means; and we find that they hang by a bent stalk, 

 attached to a flattened, ovoid, brown organ, having a cleft which 

 catches the claws or tarsal hairs, or the fine hairs surrounding the 

 trophi, of insects climbing over the umbels. 



With most of the plants of this kind now known, fructification 

 may be brought about by the aid of more than one species of insect; 

 and none, perhaps, off"er a more striking instance of dependence, or 

 more curious floral mechanism to allure, than do the Orchids. They 

 display an infinitude of curious contrivances and adjustments for the 

 purpose. In the genus Jlahenaria^ for instance, the peculiarities of 

 which are described by Dr. Gray, we find flowers that, in some cases, 

 strongly recall butterflies ; a separate pocket for the nectar; the pol- 

 len bound together in masses by elastic threads, so as to lessen the 



* See Darwin's "Animals and Plants," etc., II. p. 132. 



