EUPHORBIA VI ROSA AND ALOE DIGHOTOMA 43 
angles of the branch are beset by short curved thorns ; they run longitudinally, 
rarely spirally, from base to apex ; they are separated by broad shallow grooves 
m which the assimilating tissue is concentrated and protected by an epidermis 
with a smooth thick cuticle. Of the three plants used in the experiments, A 
and C were m fruit ; B was a young plant about H feet high, which apparently 
had not yet flowered ; all were leafless. 
The diameter of a normal branch is from 1 ^—2 inches, ot which considerably 
more than half is occupied by the pith ; this tissue is broken up by a series of 
Photograph 2. Stem of Euphorbia virosa, in longitudinal section. 
(Photograph of freshly-sectioned living stem.) 
large air-cavities separated from one another by diaphragms of parenchy- 
matous tissue containing ramifications of the latex-system 1 (Photograph 2). 
So great a development of air-spaces in a succulent plant is very remarkable 
and appears at the moment to be unique. 
The general form of Aloe dichoioma is sufficiently well known (Photo- 
graph 3). The smooth, shining, greyish -ye flow bark ot the trunk must have 
1 See Worsdell, ’14. 
4—2 
