DESCRIPTION OF THE ORCHID FLOWER. 253 



are concealed in niches, and are caused to adhere to the bodies of intruding insects 

 by means of a special organ, and are then drawn out of their hiding-places. This 

 method of transferring the pollen is especially characteristic of Orchids, and is 

 extremely interesting. It will be worth while to consider it in some detail in 

 connection with a few well-known instances, and for that purpose it will be neces- 

 sary to begin with a general description of the peculiar structure of the flower in 

 Oirehids. In all species of Orchidaceae the ovary is inferior, and at the flowering 

 season resembles a pedicel. It bears at the top two tripartite whorls of floral 

 leaves, one standing just above the other. Two segments in each whorl are alike 

 in form, whilst the third is different. The difference is most conspicuous in the case 

 of the odd segment of the inner whorl, and it is called the lip or lahellwrn. Often 

 it really resembles a lip, but not uncommonly it assumes the shape of a sabot, boat, 

 or basin, whilst, in other cases, it is like an outstretched tongue, or even the body 

 of a spider or insect (see fig. 257 ^ p. 226 and Plate XIII.). The labellum is fre- 

 quently lobed, and may also be fringed or slit up into long curling strips. In fact 

 it exhibits an endless variety of configuration, and to it is mainly due the extra- 

 ordinary appearance characteristic of Orchids. The ovary itself is produced in 

 most Orchids above the two perianth-whorls, and rises up in the middle of the 

 flower as the so-called colwmn. This structure, which bears the stamen and the 

 stigmatic surface, is always opposite the labellum, so that the approach to the 

 bottom of the flower lies between the two. There are two stamens in the few 

 Orchids allied to the already-mentioned Lady's Slipper (Gypripedium; see figs. 267^ 

 and 267^), but throughout the others only one stamen in each flower develops 

 pollen. The filament can only be identified by careful examination and dissection 

 of the flower; externally it is not visible. Usually the anther or pair of anthers 

 is imbedded in pits or recesses in the column, or is adnate to one face or to the top 

 of the column. In the flowers of the Helleborine {Epipadis latifolia, fig. 268 ^), 

 and many other Orchidacese, on either side of the one stamen, which has a fully- 

 developed biloeular anther, may be seen an abortive stamen in the form of a tri- 

 angular tooth. The column bears, in addition to the stamens, a stigmatic surface 

 corresponding to the tips of the three carpels. In the group of Orchids represented 

 by the Lady's Slipper {Gypripedium) all three are capable of taking up pollen; 

 in all other Orchids only two stigmas are receptive, and they are usually merged 

 together into a single disc or plate; the third stigma being transformed into the 

 so-called rostellwm, a structure which plays an important part in connection with 

 the processes now to be described. The rostellum assumes the most various forms 

 in different Orchids, and special relations subsist between it and the anther. In 

 many cases the rostellum is a beak-like structure, situated betwixt the solitary 

 stamen and the stigmatic surface; it marks, so to speak, the frontier between these 

 two structures. Certain portions of the rostellum disintegrate, forming a tough 

 and extremely sticky mass like bird-lime, which, in most cases, takes the form of 

 a wart. The anther is biloeular. The loculi contain each a clavate pollen-mass or 

 polUnium, and open betimes — often, indeed, before flower is open. After dehiscence 



