204 
Parkin.—Observations on 
formed in primary growth have their globules in suspension 
in the latex, of a different composition from those arising 
in the secondary tissues. 
In many plants this so-called viscin seems to occur 
throughout the laticiferous system, e. g. the common bread¬ 
fruit (Artocarpus incisd) and jak (A. integrifolia )—trees of 
the tropics. 
Most likely there are bodies which do not come within 
the categories of caoutchoucs and guttas, and yet are hydro¬ 
carbons with the same percentage composition. Probably 
some of these viscous substances are such. Also it appears 
probable that all caoutchoucs are not identical, and that when 
prepared as pure as possible from the latex, as by the 
ingenious centrifugal method of Biffen, it may be found, for 
example, that the caoutchouc of Hevea has slightly different 
properties from that of Castilloa . 
V. Effect of previous wounding on the Flow 
of Latex. 
An important fact connected with the tapping of Hevea 
trees, and a remarkable one from a botanical point of view, 
is that wounding the bark causes a greater flow of latex from 
subsequent injuries. 
Mr. Willis \ in his experiments on the yield of these trees, 
found that the weight of rubber obtained from the second 
tapping of a series of trunks was about double that obtained 
from the first incisions. Further experiments have shown 
that this increase in weight is due to a much greater flow 
of latex, from fresh wounds in a tree recently tapped, than 
in one hitherto intact. 
One of our experiments indicated that it is possible to 
increase the quantity of latex to as much as seven times that 
obtained at the first tapping, using the same number and 
kind of incisions on each occasion. This fact we have found 
1 Willis, Rubber Cultivation in Ceylon. Circular R. B.G. Ceylon, Jan. 27, 
1898. 
