Chap. IX. GRADATION OF ORGANS. 259 



tied together in the Ophreae, and which run far up 

 inside the waxy masses of the Vandeae, are also of a 

 different nature from the cementing matter ; for the 

 threads are acted on by chloroform and by long im- 

 mersion in spirits of wine ; whilst these fluids have no 

 particular action on the cohesion of the waxy masses. 

 In several EpidendresB and Yandeae the exterior grains 

 of the pollen-masses difter from the interior grains, in 

 being larger, and in having yellower and much thickei 

 walls. So that in the contents of a single anther-cell 

 we see a surprising degree of differentiation in the 

 pollen, namely, grains cohering by fours, then being 

 either tied together by threads or cemented together 

 into solid masses, with the exterior grains different 

 from the interior ones. 



In the Vandeae, the caudicle, which is composed of 

 fine coherent threads, is developed from the semi-fluid 

 contents of a layer of cells. As I find that chloroform 

 has a peculiar and energetic action on the caudicles 

 of all Orchids, and likewise on the glutinous matter 

 which envelopes the pollen-grains in Cypripedium, 

 and which can be drawn out into threads, we may 

 suspect that in this latter genus, — the least differenti- 

 ated in structure of all the Orchideae, — we see the 

 primordial condition of the elastic threads by which 

 the pollen-grains are tied together in other and more 

 highly developed species.* 



* Auguste de Saint Hilairc drop by drop into the anther. 



('Lemons de Botaniqne,' &c.. 1841, Had not so eminent an authority 



p. 447) says that the elastic threads made this statement, I should not 



exist in the early bud, after the have noticed it. It is ccrtiiinlv 



jjoUen-grains hiive been partly erroneous. In buds of Epipactis 



formed, as a thick creamy fluid. latifoUa I opened the Muther, 



He adds tliat his observations on whilst perftctly clos; d and free 



Ophrys apifera have shown him from ihe rostelluin, and found the 



that this fluid is secreted by the pollen-grains united by elastic 



robtellum, and is slowly forced threads. Ccvhalajithcrn <jrandi' 



