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 actions' for 1854. Dr. Hooker has given a full and accurate account, with drawings, of the structure of the parts; but from not having attended to the agency of insects, he did not fully understand the object gained. Robert Brown, in his celebrated paper in the 'Linnean Transactions,' expresses his belief that insects are necessary for the fructification of most Orchids; but adds, that the fact of all the capsules on a dense spike not infrequently producing seed, seems hardly reconcilable with this belief: we shall hereafter find that this doubt is groundless. Many other authors have given facts and expressed their belief, more or less fully, on the necessity of insect-agency in the fertilisation of Orchids.

In the course of the following work I shall have the pleasure of expressing my deep obligation to several gentlemen for their unremitting kindness in sending me fresh specimens, without which aid this work would have been impossible. The trouble which several of my kind assistants have taken has been extraordinary: I have never once expressed a wish for aid or for information which has not been granted me, as far as possible, in the most liberal spirit.

EXPLANATION OF TERMS.

In case any one should look at this treatise who has never attended to Botany, it may be convenient to explain the meaning of the common terms used. In most flowers the stamens, or male organs, surround in a ring the one or more female organs, called the pistils. In all common Orchids there is only one well-developed stamen, which is confluent with the pistils, and they