196 THE ORCHID REVIEW. [JuLy, 1909. 
and the rostellum is hinged and flap-like over the stigma. The lip is 
united to the margins of the column, forming a tube, and is furnished about 
the centre with a large crest, consisting of a series of imbricating scales 
pointing downwards, which offer no impediment to an insect entering the 
flower, but compel it on retreating to press against the column, thus 
ensuring the removal of the pollen masses. On visiting a second flower the 
pollen would inevitably be left on the stigma, for the flap-like rostellum is 
lifted up and the stigma exposed. It is noteworthy that in Central America 
the native home of the Vanilla, the flowers are fertilised by small bees, but 
elsewhere, where the plant is cultivated for economic purposes, artificial. 
fertilisation has to be resorted to. Other peculiarities are that the fruit is 
fleshy, and the seeds have a crustaceous, smooth, not reticulated testa. 
There are many species of Vanilla, the genus being widely dispersed 
through the tropics, but the majority are of no economic importance. 
Galeola is an allied genus of leafless saprophytes, having fleshy fruits and 
winged seeds. The whole plant is yellow, brown, or sometimes reddish in 
colour, the inflorescence much branched, and the flower approaching Vanilla 
in structure. The genus ranges from India to Australia, and contains about 
a dozen species. 
The subtribe Diuridez, as defined by Bentham, is for the most part 
Australasian, with a few species extending into the Indo-Malayan region. 
They are very rarely cultivated. Bentham remarks that they approach 
Arethusez in their vegetation characters and Spiranthez in their erect 
anther. There are just over twenty Australasian genera and some 200 
species. They are terrestrial, and the rhizome is generally more or less 
tuberiferous, with simple erect stems, in some cases producing several 
leaves, in others only a single one, a very few being leafless. The spike or 
raceme is simple and terminal. The anther is erect or leaning forward, and 
the rostellum is terminal and erect, very often short, but sometimes as long 
as theanther. The pollen is powdery or granular, sometimes so compact 
as to appear solid, in some genera free, in others attached to the rostellum. 
The perianth also shows the greatest diversity in shape and structural 
details, as may be seen by the numerous excellent figures given by 
Fitzgerald in his Australian Orchids. Lindley placed some of the genera in 
Arethusee and others in Neottiez, but there is such a marked similarity and 
gradation between the different genera as to suggest for them a_ single 
origin, and as the Indo-Malayan species are very few in number and generally 
closely allied to Australian ones, Bentham suggests for the whole group an 
Australasian origin. The progressive development of the genera has not 
yet been worked out. The group is well represented in New Zealand and 
New Caledonia. 
(To be continued.) 
