Chap. IX. GRADATION OF ORGANS. 255 



discs touching and affecting each other's shapes, but 

 not actually joined — in Orchis latifolia and maculata 

 two quite distinct discs but with the pouch still 

 sliowiug plain traces of division ; and, lastly, in 

 Ophrys we have two perfectly distinct pouches, in- 

 cluding of course two perfectly distinct discs. But 

 this series does not indicate the former stej)s by which 

 a single rostellum became divided into two distinct 

 (jrgans ; on the contrary, it shows how the rostel- 

 lum, after having been anciently divided into two 

 organs, has now in several cases been reunited into 

 a sinijle oro-an. 



This conclusion is founded on the nature of the little 

 medial crest, sometimes called the rostellate process, 

 between the bases of the two anther-cells (see fig. 1, 

 B and D, p. 8). In both divisions of the Ophrese — 

 namely the species having naked discs and those 

 liaving discs enclosed in a pouch — whenever the two 

 discs come into close juxta-position, this medial crest 

 or process appears.* On the other hand, when the two 

 discs stand widely apart, the summit of the rostellum 

 between them is smooth, or nearly smooth. In the 

 Frog Orchis (Peristijlus viridis) the overarching sum- 

 mit is bent like the roof of a house ; and here we see 

 the first stage in the formation of the folded crest. In 

 Herminium monorchis, however, which has two separate 

 and large discs, a crest, or solid ridge, is rather more 

 plainly developed than might have been expected. 

 In Gymnadenia conopsea, Orchis macidata, and others, 

 the crest consists of a hood of tliin membrane ; in 



* Professor Babin^ton ('Manual from the other genera of Ophreao. 



of British Botany,' 3rd edit.) uses The group of s\nva\ vessels, pro- 



tiie e.xistenee of this "rostellate perly lielouging to the ro.-tellum, 



jirocess " as a character to separate runs uj), and even into, the base 



Orchis, Gymnadenia, and Aceras of this crest or proces.'<. 



