174 
REVIEWS. 
THE FERTILIZATION OF ORCHIDS.* 
MONG the points raised by Mr. Darwin in his celebrated work “ On the 
Origin of Species ” was the doctrine of the necessity of frequent or 
occasional cross-fertilization in the case even of plants whose flowers con- 
tain both stamens and pistils within the same set of envelopes. Several 
interesting cases in illustration of this principle were subsequently brought 
forward by Mr. Darwin himself ; and in our last number we called attention 
to the publication by him of a most important series of observations in which 
the beneficial effects of such intercrossing, usually effected in nature by 
insects, were demonstrated beyond a doubt ; but the first independent work 
in which the subject was treated by Mr. Darwin, was his treatise on the 
fertilization of orchids published in 1862, a second edition of which, embrac- 
ing the later researches of the author, and the results obtained by many other 
observers, has lately appeared. Although this is only a second edition, the 
interest attaching to the subject, and the length of time that has elapsed 
since the appearance of the first edition, induce us to give a somewhat 
lengthened notice of it. 
Whilst there was much a priori probability in the assumption that the 
occasional cross-fertilization of hermaphrodite flowers was a law of nature, a 
probability which received strong support from the observations of Mr. 
Darwin and others upon various plants, and the part played in the process 
by insects was not very doubtful, seeing that in most cases the influence of 
the wind could hardly be involved, and it is a matter of daily experience 
that flower-haunting insects are constantly dusted with pollen which they 
must necessarily convey from one flower to another, it was still a matter of 
considerable interest to find some plants in which this method of fecundation 
was a demonstrable necessity. Curiously enough the absolute evidence 
required was first obtained by the study of a group of plants in which the 
flowers are so singularly constructed that the stamens and pistils appear to 
form a single organ, and in which therefore the conditions for self-impreg- 
nation might at the first glance be supposed to be especially secured. In the 
orchids, in fact, the two cells of the usually single anther are imbedded in a 
portion of the pistil which stands up above the effective stigma, the whole 
* u The Various Contrivances by which Orchids are fertilised by Insects.” 
By Charles Darwin, M.A., F.R.S. A Second Edition, revised. Sm. 8vo, 
London : John Murray. 1877. 
