SEPTEMBER, 1912.| THE ORCHID REVIEW. 263 
for its nourishment. These aérial roots wind round the branches, often 
extending for yards, and clinging so tightly to the bark as to mould them- 
selves to every little inequality, and often ultimately hang free in the air, 
doubtless for the purpose of absorbing moisture, as in Rodriguezia and some 
of its allies. In some of the genera provision for storing water takes the 
form of pseudobulbs, of very various shapes, in others the only means of 
storage is the thick, leathery leaves, in which evaporation is reduced to a 
minimum; both being contrivances by which moisture is retained through 
seasons of drought. The Sarcanthez rely entirely upon their leaves for 
storage purposes, there being a complete absence of pseudobulbs through- 
out the group. Here also another remarkable development is seen, some 
of the genera being able to exist without leaves, as Tzniophyllum and 
Chiloschista in India and Malaya, Dendrophylax and certain species of 
Campylocentrum in Tropical America, and some of the Angracums in 
Africa and Madagascar—the all-essential chlorophyll being in these cases 
developed in the roots. If we compare such an Orchid as Dendrophylax 
funalis, organ by organ, with the primitive Neuwidia, we might wonder 
what characters the two possess in common, yet, as we have already seen, 
they are connected by a long chain of intermediates, through which every 
intermediate phase of progressive development can be traced. 
We have now seen that Orchids have been developed along two distinct 
lines, first by adaptations to insect fertilisation, and these of an ever- 
increasing degree of complexity, and, secondly, by adaptations to an 
epiphytal mode of existence, with the necessary modifications of the organs 
of absorption and nutrition, and a diversified set of provisions for storing 
water against seasonal periods of drought. | 
These considerations necessitate our attaching a supreme value to the 
organs of fertilisation in any natural system of classification, and this leads 
to a brief reference to the system of classification by vegetative characters 
proposed by the late Professor Pfitzer. After separating the Ophrydez, 
which were made to follow the Diandrae—where they are certainly out of 
place—the next primary division adopted was that into Sympodiales and 
Monopodiales, according to whether the inflorescence was terminal or 
lateral. In the Sympodiales the growth is terminated by an inflorescence, 
after which a new lateral shoot is produced, but in the Monopodiales the 
stems continue to grow for a number of years at the apex, and the 
inflorescence is lateral. But Pfitzer himself admits that the monopodial 
type is not monophylitic, and remarks that the monopodial Huntleyine are 
very near the sympodial Zygopetaline, and may have been derived from 
them. Bentham, indeed, included Huntleya under Zygopetalum, which is, 
perhaps, an extreme view. The fact is the monopodial mode of growth 
only came in after the adoption of an epiphytic habit. It is a purely 
