I lO 
Briefe. 
capsules. The species is interesting in some other respects also. The bifid pedi- 
celli of the poUinia execute the same movement, you have described in Maxiilaria 
ornithorhyncha, the right and left poUen masses are connected by an elastic tissue 
like that of the caudicle. 
Whereas in all other Vandeae, I examined (Notylia, Cirrhaea, Ornitho- 
cephalus, Polystachya, Aeranthus, Oncidium, Cyrtopodium and several other 
species of Maxillaria), the margins of the valves of the seed - capsules are 
beset with hygroscopic hairs, I could not find them in the ripe pods of 
this species; but there are some scattered and rudimentary hairs in the young 
capsules. 
I send you poUen-tubes taken out of a young pod of this Maxillaria showing 
the fringes which from the six longitudinal ribbons extend between the ovula. 
On comparing these pollen-tubes with those of Cattleya Leopoldi you will be 
Struck by a remarkable difference. 
In Maxillaria (and with a single exception in all our Vandeae) the pollen- 
tubes remain fresh in their whole length; in Cattleya (as well as in all our Epi- 
dendreae) the Upper part of the pollen-tubes soon becomes dry ar)d black ; this 
evidently is a consequence of the stigmatic Chamber being shut in Vandeae, 
whilst it remains open and the pollen exposed to air in Epidendreae. 
I already told you in my last letter, that in Notylia and in Oncidium 
flexuosum, pollen and Stigma of the same plant act, as it were, as a poison on 
each other; this is also the case with the curious Oncidium unicorne and with 
another species which seems to be nearly related to Oncidium pubes. 
I have had numerous racemes of a second species of Cirrhaea (perhaps the 
C. dependens Rchb. f.) interesting by the extreme variability of the colours of its 
flowers. I could not fertilize this species with fresh pollinia whilst it might be 
done easily after they had dried half an hour or an hour. This probably will 
prevent the flowers being fertilized with the same plants pollen. The disk in this 
species is provided with a hook facilitating its being taken away. 
There begins now to flower here a curious small Orchid, viz Ornitho- 
cephalus^). The anther-bed has a small transverse ridge on the anterior margin; 
the pedicellus of the pollinium passing over this ridge forms an obtuse angle; as 
soon as the pollinium is removed by an elastic binding of the pedicellus, this 
obtuse angle is transformed into a very acute one and subsequently by an hygro- 
scopic movement, the pedicellus is curved in a very singular and elegant manner. 
In water the pedicellus returns to the former form. The two pods of Monachanthus 
which I fertihzed (Dec. 25) with pollen of Catasetum mentosum are now already 
7 cm long and as much in circumference. 
The plant of Oncidium flex., on which I had fertilized some flowers simulta- 
neously with pollen from a distinct plant of the species and with pollen of Epi- 
dendrum Zebra, having perished by an accident I have repeated the experiment 
on another plant; the result has been the same and I have satisfied myself that 
it is indeed the side of the Epidendrum-poUen which grows less and that of the 
Oncidium-pollen which grows more rapidly (Fig. 34). 
I) S. die Tafel in Darwin, Fertilization of Orchids, p. 159, 160. Ferner Brief an Hermann 
Müller vom l. Juli 1866, S. 86. 
