158 
Groom. — On the Functions 
their results merely show that changes do take place in the 
constitution of the latex. Starch, for instance, does disappear 
to a certain extent under the conditions of the experiments. 
These results may have been partly pathological, though not 
wholly so, because some of the changes recorded take place 
naturally during the life of the plant. But no proof was 
offered to show that the substances were used as food. Again, 
Hansen 1 concludes that the apparently useful ferments found 
in latex are useless excretions which merely happen to act as 
ferments. On the other hand, Van Tieghem 2 and Mdlle. 
Leblois 3 are of opinion that the laticiferous tubes are excretory 
in nature. The former goes so far as to suppose that all the 
constituents of latex are useless excretions. He points out that 
starch in the guard-cells of the stomata of fallen leaves, and 
the sugar in fleshy fruits, are true excretions. But in reality 
neither of these substances can be said in these cases to be a 
useless excretion. The sugar has a biological function, whilst 
the starch probably was manufactured for consumption. There 
is no evidence that starch or sugar can be degradation-pro- 
ducts absolutely useless to the plant. Schimper 4 dismisses 
the theory that the sugar of extrafloral nectaries is an excre- 
tion of which the plant wishes to rid itself. As further 
arguments against Van.Tieghem’s view, we may allude to the 
large quantity of starch present in the latex of young Eu- 
phorbias 5 . Also we may call attention to the fact that this 
starch does wholly or partially disappear under normal and 
experimental conditions 6 . 
On the whole it may be stated that latex mainly consists 
1 Hansen, Ueber Fermente u. Enzyme, in Arbeit, des bot. Instit. Wurzburg, 
Bd. Ill, p. 287. 
2 Van Tieghem, Second memoire sur les canaux secreteurs des plantes, in Ann. 
d. Sc. Nat. 1885. Vuillemin, Remarques sur la situation de Tappareil secreteur 
des Composees, in Bullet, soc. bot. de France, Bd. VI, p. 108, 1884. 
3 Leblois, Sur le role du latex des Composees, Bullet, soc. bot. de France, 
Bd. VI, p. 122, 1884. 
4 Die Wechselbeziehungen zwischen Pflanzen und Ameisen im Tropischen 
Amerika. Jena. 1888. 
5 Treub, loc. cit. 
6 Schullerus, loc. cit., und Treub, loc. cit. 
