178 
POPULAR SCIENCE REVIEW. 
as already indicated, by the insertion of some suitable pointed object into 
the orifice of the nectary in the common purple orchis ; after their removal 
the change of position may be directly observed ; the fact that the whole of 
these operations are effected in nature by the agency of insects, is demonstrated 
by the frequent presence upon their heads and proboscides of the pollinia of 
various species of orchids ; and these facts, coupled with the position assumed 
by the pollinia when thus attached, adapting them for being brought into 
direct contact with the stigmas of other flowers, and with the impossibility 
in most species of the pollen reaching the stigma by any other means, may 
be regarded as furnishing an irrefragable body of evidence, from which we 
may with no great difficulty infer that the whole of these contrivances, so 
wonderfully correlated as they are, are directed to one special object, namely 
the fecundation of one plant by the pollen of another. For the advantages 
gained by the intercrossing of distinct individuals of plants, the reader may 
consult Mr. Darwin’s book, “ On Cross and Self-fertilization,” noticed in our 
last number, in which one side of the question at all events is thrown into 
high relief j perhaps the broadest and most general effect of this intercrossing 
of individuals of the same species is to keep the species “ true,” by its tend- 
ency to efface indifferent individual variations. 
But whatever opinion we may form as to the purpose in nature of this 
apparent necessity for at least an occasional intercrossing of individuals of 
the same species of plants, there can be no doubt that in nearly all the 
orchids we find what may be called most careful provisions made to secure 
that the fertilization of the ovules in a given ovary shall not be effected by 
the pollen of the same flower, nor in a general way, by that of the same 
plant. The number of known self-fertilizing species is very small ; they 
will be found referred to in Mr. Darwin’s book. In all the rest the flower 
shows “contrivances,” as Mr. Darwin calls them, for securing the removal 
of the pollinia by insects visiting the flowers, although the precise nature 
of these arrangements is by no means the same in all. 
Several species of Orchis show the same arrangements as Orchis masculct 
just described, and it would appear that bees, humble-bees, and flies are the 
chief agents in transporting the pollinia of these species. In the Pyramidal 
Orchis ( 0. pyramidalis ) the general arrangement of the parts is very similar 
to that which occurs in O. mascula, but the caudicles of the pollinia, instead 
of being attached to two separate membranous discs separated from the 
upper and posterior surface of the rostellum, are affixed to a single saddle- 
like piece, representing the two discs above mentioned united, and this, 
which is also strongly viscid beneath, not only adheres by its under surface 
to the object that sets it free by pushing down the pouch of the rostellum, 
but actually clasps and embraces the object, which, in nature, is usually th& 
proboscis of some moth or butterfly. This clasping not only aids in fixing 
the pollinia to their means of transport, but also serves to produce a diver- 
gence of the pollinia, which, by this means and by the subsequent contrac- 
tion of the membrane (as in O. mascula ), are brought into a proper position 
for contact with the stigma of another flower. The moths and butterflies- 
which frequent these flowers, are actually compelled to insert the proboscis 
into the nectary in such a direction as will bring them into contact with the- 
rostellum, by means of certain guiding plates placed on the labellum, and in 
