Chap. IX. GEADATION 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 

 showing plain traces of division; and, lastly, in 

 Ophrys we have two perfectly distinct pouches, in- 

 cluding of course two perfectly distinct discs. Bu^ 

 this series does not indicate the former steps by whic? 

 a single rostellum became divided into two distinct 

 organs ; 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 single organ. 



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 

 having 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 {Peristylus 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 Gijmnadenia eonopsea, Orchis macidata, and others, 

 the crest consists of a hood of thin membrane ; in 



* Professor Babingtou ('Manual from the other genera of Ophreaj. 



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



the existence of this "rostellate perly helonging to the rostellum, 



process " as a chiiracter to separate runs up, aud even into, the base 



Orchis, (iymnadcuia, and Aceras of this crest or process. 



