116 ORCHIDS. 
anthus nigricans are rather of a rich red tinge. This Orchid is also 
remarkable as almost our only one of copious occurrence in sandy 
desert-country unless perhaps Microtis porrifolia. In drying this 
plant turns completely black. All the above-mentioned genera 
of the Caladenia-group have the labellum almost or quite sessile. 
This note affords at once the means of separating them from a 
series of genera with a distinctly stalked labellum, to which 
Pterostylis and Caleyana here belong. Both these are further 
singular for the irritability of their labellum, which in Pterostylis 
protrudes downwards, but on the slightest touch snatches upwards 
on to the upper sepals ; precisely the same movement takes place 
in Caleana, but as the flowers of that genus are turned upside 
down by a twist of their stalklet, the labellum is in an erect posture 
while stretched out, and becomes deflexed by irritation. This 
extraordinary sensitiveness and spontaneous movement serve the 
purposes of fertilization, as insects become thus allured and en- 
trapped, when alighting on the labellum, and in their endeavor to 
escape are apt to carry the pollen to the stigma of the same flower, 
or by touching the viscid stigmatic fluid and subsequently the 
anthers, may fix the pollen-masses to any portion of their body and 
carry them to the stigma of flowers of another individual plant or 
effecting hybridisation to another species. In a superb work, 
commenced by Mr. Fitzgerald, on the Orchids of New South 
Wales, many observations also are recorded on the fertilisation of 
these plants, irrespective of descriptive details, which accompany 
the splendid illustrations. Pterostylis differs from Caleana further- 
more in the broadness of the upper sepal, to which is added by 
the adherence of the lateral sepals, also in the concrescence of the 
lower sepals and in the winglike expansions of the genitalial 
column, from which the generic name is derived, not extending 
to the base. The green color of the flowers gives these plants also 
a strange aspect. Of Caleana, named in honor of Mr. G. Caley, a 
botanic emissary of Sir Jos. Banks to New South Wales, we 
possess only Caleyana major, and this very sparsely ; but Ptero- 
stylis is represented by at least a dozen species in our colony, all 
fully described in the Flora Australiensis, vol. vi. Of the re- 
maining genera of our Orchids Spiranthes, with one almost alpine 
