468 OR CHI DA CEAE 



the O. drop their 1. (though they may flower), and ' hibernate ' in the 

 condition of fleshy psendobulbs. One pseudobulb, which is a thickened 

 stem-internode, is usu. formed each year. In this, water and other 

 reserves are stored. Those epiphytes which do not form these tubers 

 have fleshy 1. which serve the same end ; the fleshy leaved orchids, 

 e.g. Vanilla, have usu. a very feebly developed velamen. Some mono- 

 podial forms have no green 1. at all, assimilating either by the surface 

 of the stem, or by the long dangling aerial roots (Polyrrhiza, &c.). 



The infls. are racemose, very often spikes, which look like racemes, 

 the long inf. ovary resembling a stalk. The fl. is -|- and departs from 

 -the ordinary Monocot. type. There are two chief divisions of O., 

 with different fls., the Monatidrae and Pleonaijdrae, with i and 2 sta. 

 respectively ; the great majority are monandrous. P in 2 whorls, 

 epig., petaloid. The post, petal is usu. larger 

 than the rest, and is termed the labellum ; by 

 the twisting (resitpinatioti) of the ovary through 

 180 it comes round to the ant. side of the fl. 

 and forms a landing place for insects. In many 

 O. its structure is exceedingly complex. The 

 essential organs of the fl. are all comprised in 

 a central structure by. which the O. can be 

 recognised at a glance, viz. the column, which 

 consists in the simpler cases of the combined 

 style and sta. (to use the old-fashioned expres- 

 sion ; in reality it is very probably an outgrowth F , ora , diagram of Or . 

 of the axis, bearing the anthers and stigmas at c his,beforeresupination 

 the top). In the monandrous forms the column (after Eichler, modi- 

 exhibits one anther and two fertile stigmas (often M * = 'f ellum - 



.- . i i oliJ alcltlillltJUCt 



confluent), together with a special organ, the 



rostellum, which repres. the third stigma. The single anther is the 

 ant. one of the outer whorl (if we imagine the fl. of O. derived from 

 a typical 3-merous fl.); the other two of this whorl are entirely absent, 

 and also all those of the inner whorl, though in some genera, e.g. 

 Orchis, the ant. two are repres. by stds. upon the sides of the column. 

 The two fertile stigmas are the post, pair, and the third (ant.) is repres. 

 by the rostellum (in using the terms ant. and post., the resupination 

 is supposed not to have occurred). 



The various organs face the labellum, and, in the fl. of a simple 

 O., e.g. Orchis, can easily be made out. A little above the base are 

 the two stigmas, then above these a projecting point, the rostellum, 

 and above this again, and behind it, forming the apex of the column, 

 is the anther, which shows two lobes. Each is occupied by z. pollinium , 

 or mass of pollen. Under the microscope the grains of pollen are 

 seen to be tied together in packets by elastic threads; these unite at 

 the base of the pollinium and form a cord, the candicle, which runs 

 down into, and is attached to part of the rostellum. 



The simple construction found in Orchis, &c., as thus described, 

 is replaced by much more complex arrangements in many. The 

 labellum itself may be rendered very complex, by the additioa of 

 spurs and other outgrowths ; often outgrowths of the summit of the 

 receptacle take place, displacing some of the organs, thus for example 



