Cc. A. BARBER. 31 
outer layer of wood with its layer of cambium being treated 
exactly as if it were a sclerotic band (Plate X, fig. 4). The 
scattered bast bundles in the wood of the root of Strychnos 
Nuz-Vomica do not appear to materially affect the course of 
the sucker. 
The vessels opposite to the sucker are, for the most part, 
filled with gummy substance of varying colour. In a few 
cases a dense black pigment is present.—_Azima tetracantha, 
Mallotus distans, Strychnos Nuax-Vomica, Barleria buxifolia. 
Thyloses occur in the vessels of certain species and are of spe- 
cial interest in two cases. In Vernonia travancorica and Argy- 
reia speciosa they become thick-walled and pitted (Plate IX, 
figs. 3 and 4),a single thvlose sometimes filling up a vessel soas 
to present the appearance of one vessel inside another. In Ver- 
nonia travancorica, some of the thyloses are filled with crystals 
of calcium oxalate (fig. 2). 
20. Action of the Secretion on Starch.—This has already 
been referred to (Sant. II, 33 and Olaz, para. 17), and it was 
demonstrated from a study of many sections that the ferment 
was more active in the destruction of cellulose cell walls than 
of their starchy contents. The study of the sections of Cans- 
jera Rheedi haustoria leads to the same conclusion, and the 
following remarks may be added to those already made. 
In the rapid progress of the sucker through the cortex 
the starch grains are of minor importance, the object being 
presumably to penetrate the tissues as soon as possible by the 
solution of the cell-walls. Starch grains are thus not infre- 
quently found in the yellow mass of substance formed by the 
outpouring of secretion from the glandular cells and the break- 
ing down of the cell-walls. But this is not all. In not a few 
cases there appears to be a definite accumulation of starch in 
this layer when no such substance is to be found in the neigh. 
bouring cells. In other cases, there is a dense mass of starch 
in the woody cylinder exactly opposite the sucker end, while 
there is none in the rest of the root attacked, This is the case 
3 
