JuLy, 1909] THE ORCHID REVIEW. 195 
sepals and petals are coherent below, and arch over above, while the lip is 
recurved beneath, thus forming a landing stage for the insect immediately 
in front of the mouth of the tube. 
The character of having powdery pollen and the anther free from the 
rostellum is characteristic of numerous other genera, which Lindley grouped 
. together in a distinct tribe, under the name Arethusez, but which 
Bentham afterwards united with Neottiez, partly because of the difficulty of 
placing some of the genera in their correct position. The Neottiez, how- 
ever, as defined by Lindley, show a marked advance in structure, as will 
presently be seen, and it seems probable that most of the doubtful genera 
will fall into their natural positions when better known. The majority are 
not known in cultivation, and the pollinia, from their very nature, are 
difficult to make out from dried specimens. A few are also colourless 
saprophytes, and the affinities of these degraded types are not always easy to 
make out, even when the plants themselves are well known, and the latter is 
not always the case. 
Lindley divided the tribe Arethuseze into three smaller divisions, 
Euarethusez, Vanillez, and Gastrodiez, but the latter consists of two 
genera of leafless saprophytes, Gastrodia and Epipogon, which have sectile 
pollinia, and the latter has the pollinia attached to a rostellar gland, both 
characters indicating a higher degree of specialisation. In Euarethusez he 
included Pogonia, with the allied genera since included in it, Calopogon, 
Arethusa, the Chilian genus Chlorza with its near allies Asarca and 
Bipinnula, Cephalanthera, which Darwin considers a degraded type close 
to Epipactis, and several of the Australasian genera now referred to the 
subtribe Diuridez. Disregarding the doubtful types it is quite clear that 
here we have the most primitive genera of the Monandre. They are all 
terrestrial plants, with comparatively simple structure, as in the genera 
above mentioned. 
Lindley’s other division of the Arethusez is Vanillee, in which he 
included Vanilla, Epistephium, Sobralia, and the genera now included 
under Galeola. In the structure of the column and pollinia the genera of 
Vanillez closely resemble Euarethusez, though in habit there are marked 
differences. Sobralia is a genus of reed-like plants, in habit closely 
resembling Selenipedilum, with plicate, strongly-ribbed leaves, and showy 
terminal Cattleya-like flowers, and having the segments more or less united 
at the base. Epistephium is pretty similar in habit, but has a small 
cupulate calyculus at the base of the segments. Vanilla is a genus of 
tropical climbers, often ascending to the top of the tallest trees, and there 
producing spikes of green or sometimes yellowish flowers. The fruit of 
Vanilla planifolia is aromatic and furnishes the Vanilla of commerce. The 
pollen grains of Vanilla are not united by threads but by viscous matter, 
