77 



attached to a minute separable gland ; a trace of this struc- 

 ture also exists in P. luteola, and is probably what Sir W. 

 Hooker saw when making the drawing afterwards published 

 in his Exotic Flora. At first sight a fact like this would 

 appear either to weaken the value of the distinction by which 

 Orchidaceous plants of the Vandeous are separated from 

 those of the Malaxideous division, or to render it necessary 

 to transfer Polystachya from the latter to the former- But 

 upon an attentive examination of the structure of the process 

 in question, it is seen that it is not a cartilaginous elastic 

 strap, adhering to a hard gland with a well defined outline, 

 but a collection of large cells, loosely cohering, very convex, 

 and filled with air ; while the representation of the gland is 

 a small hemispherical succulent mass, to which the cellules 

 adhere. This process may therefore be regarded as a mere 

 modification of the shapeless viscid matter to which the 

 pollen-masses of many Malaxideous genera are attached. 



Mr. Loddiges, in sending the above plant, accompanied it 

 with specimens of Polystachya luteola from the West Indies 

 and Ceylon, with the remark that those plants were impro- 

 perly considered as the same species. Upon a careful re- 

 consideration of their structure I have come to the conclusion 

 that this opinion is well founded, and that they are to be 

 distinguished upon sufficient grounds. In fact the pro- 

 bability of a difference existing between the Western and 

 Eastern plants had occurred to me when writing the first 

 part of the Genera and Species of Orchideous Plants, but I 

 had no materials which would enable me to point out in 

 what the difference consisted, except in colour. Upon a 

 comparison of the live plants with each other, it now appears 

 that the Eastern plant is much taller, with long lateral 

 branches, that its flowers are smaller and yellower, with a 

 tinge of purple, while the Western plant has pale watery 

 green flowers ; that its lip is wider, with the middle lobe 

 rounded, and the disk furnished with a smooth oblong callo- 

 sity projecting from among the down, which otherwise covers 

 it, while the other has the middle lobe more wedge-shaped 

 and the disk completely buried in down ; finally, that the 

 spaces between the ribs of the ripe fruit are plainly reticu- 

 lated in the species from Ceylon, but free from reticulations 

 in that from the West Indies. The two plants may therefore 

 be separated for the future by the following diagnoses. 



