AvuGuST, 1909.) THE ORCHID REVIEW. ast 
limits of a single group, and that species having primitive characters in one 
part of the flower may show a high degree of specialisation in others. 
The subtribe Vanillez is very similar to Arethusez in the structure of 
the anther and pollinia. Bentham includes in it the genus Vanilla, which 
is widely diffused through the tropics, Galeola, extending from India and 
Japan to Australia, Eriaxis, a monotypic genus from New Caledonia, with 
the American genera Epistephium, Sertifera and Sobralia. 
Vanilla differs completely in habit from anything we have yet considered. 
It is a genus of tall climbers, and-the much elongated. fleshy stems produce 
aérial roots at the nodes, which besides absorbing nutriment act also as ten- 
drils in supporting the climbing stems. The flowers are borne in racemes 
or clusters toward the apex of the stems, and are very complex in structure. 
The lip is united to the margins of the column for a considerable distance, 
and then reflexes at the mouth, forming:a tube and a landing stage on which 
the fertilising insects alight. These, according to Deltiel, are small bees of 
the genus Melipone, which visit the flower for the honey which is copiously 
secreted at the base of the tube. The disc of the lip bears a crest consisting 
of imbricating scales. pointing downwards, and forming a sort of stiff hinged 
brush, which would allow an insect to enter the flower, but on retreating 
cause it to press closely against the column. There are two prominent 
column wings, and the stigma is situated beneath the flap-like rostellum. 
The pollen grains are simple, and held together by viscid matter, not by 
elastic threads. The insect on retreating from the flower would first push 
back the flap-like rostellum and then bring away the pollen messes, and 
when the process was repeated on another flower the latter would adhere to 
the stigma. V. planifolia, the Vanilla of commerce, is a native of Central 
America, where the flowers are fertilised by small bees, but elsewhere hand 
fertilisation has to be resorted to. The genus contains over fifty species, and 
in one small section of about a dozen species the plants have become leafless 
the work of nutrition being carried on by the chlorophyll in the green fleshy 
stems. The genus may be said to combine the terrestrial and epiphytic 
habit, for the plants grow in the first place in the soil, but derive part of 
their food from the aérial roots produced by the stems. The fruits are 
fleshy, and the seeds roundish, with a smooth shining crustaceous testa. 
~ Galeola isan allied genus of terrestrial leafless saprophytes, which Ridley 
remarks appear in the most unexpected places, sometimes covering old 
stumps, or climbing up the tree trunks in thick jungle, sometimes in hot 
and exposed grass fields, and even clambering on the roofs of native huts. 
The stems also produce aérial roots, and the flowers are borne in large 
terminal panicles, and closely resemble those of Vanilla in structure. The 
fruit is capsular, and the seeds broadly winged. 
Eriaxis rigida is a very curious New Caledonia monotype, having Very 
