88 ENGLISH BOTANY. 
and in clefts of trees, procuring their nourishment partly from the atmosphere, s 
partly from the decaying organic matter that casually accumulates about their roots, 
To denote this mode of existence, and to distinguish them from “ parasites,” the tree 
inhabiting orchids are called ‘“epiphytes.’”’ No plants unfold blossoms of more 
fantastic beauty, or of odours more delicious, or colours more vivid. They a 
utterly unlike other plants, and seem to take pleasure in the widest possible diver. 
gence from all accustomed types of structure, especially in the flowers, which remind 
us of insects, birds, reptiles, and even the human figure. Several of these vegetab 
mimics reside in our own country, but the species are distributed all over the globe 
the largest number are, however, found in the tropics. In temperate countries—wher 
they are exclusively terrestrial—they ornament groves, meadows, and marshes wi 
flowers like little hyacinths. In the hot damp woods of the equatorial regions they ¢ 
chiefly aérial, decorating the trees with the highest splendours of natural jewelle 
Our great naturalist, Mr. Darwin, has written extensively on the nature and stra 
of orchids. He shows that most, if not all, of the British species require the aid o 
insects in order that the ovules may be fertilised—in other words, that an orchid 
incapable of producing ripe seed by virtue merely of its own powers, and that 
structure is actually opposed to it, and that were moths and other insects not to visi 
these plants when in bloom, they would be sterile. Moths he calls their “ marriag 
priests.”” Deviations the most extraordinary from the customary condition and siz 
of the parts appear to form no exception to the rule. Ifthe flower be so constructe 
as to require some special adaptation on the part of an insect, the insect is forth 
coming. The means by which the operation of fertilisation is performed has bee 
minutely described by Mr. Darwin, and his work “On the Fertilisation of Orchids 
is illustrated with numerous engravings, which greatly assist his readers to under 
stand his theory. He says, “Let us suppose an insect to alight on the labellum, — 
which forms a good landing-place, and to push its head into the chamber at the bac 
of which lies the stigma, in order to reach with its proboscis the end of the necte 
or, which does equally well to show the action, push a sharply-pointed common pe 
into the nectary. Owing to the pouch-formed rostellum projecting into the gangwa 
of the nectary, it is scarcely possible that any object can be pushed into it withouw 
the rostellum being touched. The exterior membrane of the rostellum then rupture 
in the proper lines, and the lip or pouch is most easily depressed. When this 
effected, one or both of the viscid balls which lie at the base of the rostellum will 
almost infallibly touch the intruding body. So viscid are these balls that whatever 
they touch they firmly stick to. Moreover the viscid matter has the peculiar chemical 
quality of setting, like a cement, hard and dry in a few minutes’ time. As the anther 
cells are open in front, when the insect withdraws its head, or when the pen 
withdrawn, one pollen-bag or both will be withdrawn firmly cemented to the obje 
projecting up like horns. The firmness of the attachment of the cement is ve 
necessary, as we shall immediately see; for if the pollen-bags were to fall sideway 
backwards they could never fertilise the flower. From the position in which the twe 
pollinia lie in their cells, they diverge a little when attached to any object. Now, h 
is endowed with a remarkable power of contraction, which causes the pollen-bag 
