"6 STUDIES IN ROOT-PARASITISM. 
Plate XI, fig. 2). But where the bands are at all continuous, 
great difficulty is experienced. This is shown in Santalum by 
the formation of compound haustoria and, in some cases, such 
as Zizyphus and various monocotyledons, the haustorium is 
frequently defeated in its attempts at penetration. The same 
applies to continuous sclerotic sheaths round the vascular 
cylinder. Progress is very slow and the haustorium is often 
found to be shrunken and moribund before entrance has been 
effected (Sant. I, Plate VI, fig. 29). 
In an ordinary attack on a dicotyledon root we may thus 
assume that the cork is lifted piece-meal, while the sclerenchy- 
matous bands are either very slowly dissolved or, more frequent- 
ly, avoided altogether. The main work left for the secreting 
cells is the dissolution of the cortex and bast, and this is 
done with great rapidity and success by the ferments in the 
haustorium. It has been pointed out that, in Cansjera, 
as in Santalum, the presence of a gland is not necessary for 
penetration, this work being accomplished by secretions from 
the ordinary surface cells, probably aided by the cells of the 
nucleus, 
The mode of penetration varies in character in Cansjera, as 
in the other haustoria examined, according to the hardness of 
the root attacked and the distribution of its thick-walled 
protective ceils. In soft roots, with loose or lightly lignified 
woody cylinder, the latter is penetrated by the sucker, either 
all over or down the medullary rays. Occasionally the sucker 
wanders between the sclerenchymatous bands in the cortex, 
but, on the whole, these irregularities are much less frequently 
met with than in Santalum and Olaz. 
18. The Sucker.—This part of the haustorium, as we have 
seen, is formed chiefly of nuclear cells in Cansjera Rheedw, and 
the cause of its rapid entry is to be put down to the great accu- 
mulation of such cells inside the young haustorium and their 
sudden expansion the moment a split is formed in the bark. 
Some of the innercortex, distinguished by the absence of starch 
