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in the plant?” That it is so there is no doubt, since Schwendener has 
actually seen it in transparent seedlings of Chelidomum. 
From this evidence we conclude that latex bears some actual 
relation to the economy of the parent, and this relation must be the 
conduction of plastic food-material. When, by some interference with 
the normal life-processes of the plant, the latex becomes poor, on the 
resumption of the normal condition it becomes again rich, and the 
richness in food material has been found to commence in the leaves 
and to exjend to the roots. We can have no stronger corroborative 
evidence than this of the supposition that the latex tubes are a path 
by which food-material is conveyed in the plant. We, therefore, 
conclude in the light of modern conceptions of the nutrition of plants 
that the laticiferous system in plants serves the purpose of conducting 
plastic food material. 
In addition, however, to containing food substances the latex 
contains bodies which are regarded as “excretory substances. The 
plant has no means by which it can excrete its useless products 
outwardly; and the excretory substances are stored in different parts 
of the plant body. Such substances are regarded as “end-products” 
in the metabolism of the cell and are incapable ol being utilised for 
purposes of nutrition. The resins, gum-resins and gum-mucilages 
are recognised as excretory products. Such substances are known 
to occur in latex; the latex tubes are, therefore, regarded as serving 
the function of excretion. The caoutchouc in all probability does 
not exist as such in the latex, but is produced during coagulation 
from simpler bodies similarly constituted chemically. It is itself a 
compound of carbon and hydrogen and is chemically comparatively 
inactive. There is, therefore, some probability that it is an end-pro- 
duct and incapable of being further utilised by the parent. Much 
more requires to be learnt, however, concerning the changes which 
occur in latex in different parts of the plant and under different 
conditions, before any accurate conclusions can be arrived at as to the 
significance of the presence of caoutchouc. 
. Enzymes have been demonstrated in the latex of some plants. 
Ficus Carica and Carica papaya (papaw) contain peptonising enzy- 
mes. The presence of an oxidase has been demonstrated in the latex 
of Hevea ; the occurrence of black latex is ascribed this enzyme. The 
presence of enzymes is significant of the occurrence of active 
changes in the latex. 
In addition to the above mentioned functions of latex two others 
occur, viz. — the sealing of wounds and the protection of the plants 
from animals. Latex containing caoutchouc coagulates quickly, and 
the coagulated mass serves to seal wounds more or less effectively. 
In some plants thejatex tubes branch close to the surface and thus 
facilitate the sealing of wounds by the juice. In other plants hairs con- 
taining latex are present on the floral bracts and are thus regarded as 
