bo 
bo 
STUDIES IN RKOOT-PARASITISM. 
To learn what really happens in these organs will, how- 
ever, have to be left until they can be studied in the field. We 
shall there perhaps be able to test whether there is any pas- 
sage of fluids in the older haustoria and, if so, by what path 
they pass upwards. Such experiments have not been possible 
up to the present. 
Before leaving the interrupted zone, it may be remarked 
that the rows of vessels in this region are fairly equidistant. The 
number of strands varies according to the amount of second- 
ary thickening which has taken place, and, in general, a fair 
idea may be obtained of the age of a haustorium by counting 
the number of strands present. In very early cases a single 
strand is seen, while, in old, distorted haustoria, it is not 
infrequent to count as many as 40 in the section on each side 
(Plate IX, fig 5). 
15. The Cambium is distinctly seen in all parts of the 
vascular system, although it is less marked towards the sucker 
than in Olax and Santalum. Its activity and length of life, 
however, seem to vary in different parts of the haustorium and, 
in this respect, Cansjera differs from both the haustoria already 
described. Speaking generally, the cambium is short-lived 
in the axial region and it probably very soon ceases to produce 
wood there, while, passing upwards, its activity increases, 
until, in the middle of the vascular loop, a great development 
takes place. This will be rendered clearer on reading the 
paragraph on secondary thickening. 
The vessels are uniform in character in the haustorium 
proper, long and narrow, richly perforated with wide, irregular 
pits which frequently extend right across the width of the 
vessel (Plate VIII, figs. 1, 2 and 5). In this latter character 
they differ remarkably from the vessels of the transitional 
region and mother root. Here the pits are small and oval and 
are arranged in regular lines over the surface of the wide 
vessel (fig. 4). Just as in Olax, while the vessels of the sucker 
present one extreme and those of the mother root another, 
