58 ORR—LEAF GLANDS OF DIOSCOREA MACROURA. 
knoten,’’ that of Psychoiria alsophila, described by Boas,* has 
a particular interest in this respect, since this species was also 
collected by Zenker in the Cameroons. : 
The. plants of Dioscorea macroura, from which the material 
for this investigation was obtained, have been in cultivation in 
the hot houses at the Royal Botanic Garden for some years; the 
tubers, from which the original plants were raised, having been 
brought from Nigeria by Dr. J. M. Dalziel, and presented by 
him, to the Garden, along with other plants from the same area. 
By adopting methods of intensive cultivation, in a moist 
atmosphere at a temperature ranging from 60 to So degrees 
Fahrenheit, it has been possible to raise, in successive seasons, 
plants of ever increasing size and vitality. Last year, the climb- 
ing stems of this species reached a length of over 18 metres, while 
the laminae of the largest leaves averaged 15 cms. long by 30cms. 
broad, with leaf-tips fully 8 cms. in length. So far, the plants 
have never flowered, but, each year, they have been singularly 
prolific in the production of stem bulbils, and these have been 
made use of to propagate the species. ‘The plant also 
perennates by means of a ‘‘nest’’ of root-tubers, which are said 
to be of a poisonous nature. 
Reference has already been made to the remarkable length of 
the leaf-tip of this species, and it will not be out of place, at 
this stage, to describe more fully the distinctive external 
features which are so closely correlated with its glandular 
nature. 
In the mature leaf, the acuminate tip is thicker than the 
lamina, is rigid, and tapers gradually from its base to the 
pointed apex, which is usually directed downwards. It may 
reach a length of 8 cms. and is about 5 mm. broad at its junction 
with the lamina. 
at the extreme tip. Between the veins. the intervening tissue 
is slightly swollen, and forms a series of cushion-like ridges, 
from four to six in number, which are yellow-green in colour 
_ and quite opaque, in contra-distinction to the leaf-lamina, 
which is of a dark green colour and more or less translucent 
They are, if anything, more prominent on the under side of 
the acumen, while, on the upper surface, each ridge is 
tudinal slit, which communicates with the 
