14 STUDIES IN ROOT-PARASITISM. 
others in the structure of the gland itself, of the collapsed 
layers and the vascular system. These parts of the haustorium 
will be dealt with in succession. 
9. The gland is a very constant feature in the haustorium 
of Olax scandens, so constant that I have not been able to 
convince myself that it is ever absent excepting in the very 
smallest. This is at variance with what was observed in 
Santalum, where the gland was frequently absent and was 
regarded rather as an additional means of penetration in difficult 
cases. 
It first makes its appearance as a dark shadow in the lower 
half of the nuclear axis (Plate IIT, fig. 2), and an examination 
of this shadow has shown us that it is caused by an accumula- 
tion of plastic materials in the cells, together with a very rapid 
sub-division into small cells transversely elongated (Plate ITI, 
2d and 2d’). 
At an early stage of the development of the gland a dark 
“cap” is seen to be formed over its upper, broader end, while 
the lower half is narrower and only imperfectly developed (Plate 
IV, figs. 1 and 2). The upper half rapidly expands, a wide clear 
‘“Jumen” being formed traversed by faint dark horizontal lines, 
the cap at the same time becoming more pronounced and clothing 
the whole of the upper half of the gland. The lower half is 
narrower, is not bounded by such a dark layer but develops a 
lumen like that above it. Below the gland a dark vertical shadow 
is traceable connecting it with the host’s root (Plate IV, fig. 2). 
It will be well to examine such a stage carefully, because the 
glandular cells quickly undergo disorganization and, in the next 
stage (fig. 3), have already lost much of their character. The 
cap is seen to consist of a great number of very small cells closely 
packed together and densely filled with dark contents, being 
sharply marked off from the cells of the nucleus outside. These 
form the “bed” of the gland, giving rise to the secreting cells 
(Plate IV, 2b x). The walls of the lower half of the gland consist 
of similar cells, but they are neither so small nor so closely 
