CHAP. VI. 
FERTILISATION. 
285 
has taken great precautions to prevent contact, by so placing 
the anther that it is next to impossible for the pollen to touch 
the stigma until the energy of the former is expended. 
Nevertheless, it is represented by Adolphe Brongniart, in a 
paper read before the Academy of Sciences at Paris, in July 
1831, that contact is as necessary in these plants as in others, 
and that, in the emission of pollen-tubes, they do not differ 
from other plants. These statements have been followed up 
by Brown, in an elaborate essay upon the subject, in which 
the results that are arrived at by our learned countryman are 
essentially to the same eifect. To these there is at present 
nothing equally positive to oppose ; but, as the indirect observ- 
ations of Mr. Bauer, and the general structure of the order, 
are much at variance with the probability of actual contact 
being necessary, and especially as Brown is obliged to have 
recourse to the supposition that the pollen of many of these 
plants must be actually carried by insects from the boxes in 
which it is naturally locked up, it must be considered, I 
think, that the mode of fertilisation in Orchideae is still far 
from being determined. I must particularly remark that the 
very problematical agency of insects, to which Brown has 
recourse in order to make out his case, seems to be singularly 
at variance with his supposition that the insect forms, which 
in Ophrys are so striking, and which he says resemble the 
insects of the countries in which the plants are found, " are 
intended rather to repel than to attract." It may be true, as 
Brown observes, that there is less necessity for the agency of 
insects in such flowers as the European Ophrydeae ; but what 
other means than the assistance of insects can be supposed to 
extricate the pollen from the cells in the insect flowers of 
Renanthera Arachnites, the whole genus Oncidium, Tetra- 
micra rigida, several species of Epidendrum, Cymbidium 
tenuifolium, Vanda peduncularis, and a host of others. Is it 
not, moreover, possible that the pollen of Orchideous plants 
may partake so far of the common properties of that form of 
matter as to be capable of emitting (imperfect ?) pollen tubes 
when brought into contact with the necessary stimulus, al- 
though it is not their general character so to do, and although 
