May, 1908. ] THE ORCHID REVIEW. 131 
ORCHIDS: THEIR STRUCTURE, DEVELOPMENT, AND 
FERTILISATION, 
Notes of a lecture given at a meeting of the Kéw Gardeners’ Mutual Improvement 
Society, held on February 17th, 1908, by Mr. R. A. Rolfe, A.L.S., and illustrated with 
lantern slides. 
(Continued from page 101.) 
Up to this point we have been dealing almost entirely with terrestial Orchids, 
but the two remaining tribes are largely epiphytic, though not entirely so. 
The Epidendrez follows next in the series, forming an enormous tribe, 
which is well represented among cultivated Orchids, including such familiar 
genera as Dendrobium, Epidendrum, Cattleya and Lelia, Bulbophyllum, 
Ceelogyne, Masdevallia, Phaius, Calanthe, and others too numerous to 
mention. Here the pollinia are seen to have taken on another stage of 
development, having become what is termed waxy. The pollen grains are 
united into masses, corresponding with the number of cells, two, four, or 
eight, into which the anther is divided, and are cemented together into waxy 
masses, which are removed bodily by the insects which fertilise the flowers. 
In some cases the pollinia are partially powdery, at least when old, and a 
few genera have been placed in both the Neottiez and Epidendree, showing 
that the transition of the one into the other is not very sharply defined. In 
many cases, however, the pollinia are hard, and not easily cut with a knife. 
Here the transition from the terrestrial to the epiphytic habit is well 
shewn, and it may be remarked in passing that it is among the former that 
the species with partially powdery pollinia are found. The Epidendrez are 
mostly tropical and sub-tropical, and the epiphytic species are found in the 
great forest regions, the epiphytic habit, with all that it implies, being an 
adaptation to enable them to exist up among the branches of the trees, 
where the necessary light, and also the insects on which they rely for the 
fertilisation of the flowers, are found. 
The change from a terrestrial habitat implies a very different method of 
acquiring their food, and it is in the nature of the roots that one of the 
greatest differences is seen. The roots of a plant serve the double purpose 
of anchoring it securely to the matrix on which it grows, and of taking up 
food for its subsistence. In terrestrial plants the roots are usually much 
branched, and finely divided, but in epiphytes these characters are greatly 
modified. In the latter the roots are generally fleshy, and except at the 
growing point are covered with a white, closely felted covering, known as 
the velamen, and they adhere tightly to the bark of the trees on coming into 
contact with them, and often wrap round them so as to give them a secure 
attachment. But they only utilise their hosts to this extent, for they are 
not parasitic like the mistletoe, but collect their own food from the moisture 
