202 
Parkin.—Observations on 
Groom 1 confirms Schimper’s work, that darkening does 
not make the starch disappear from the laticiferous tubes, and 
mentions that in Euphorbia Peplus the tubes contain starch 
till the death of the plant. 
I find that these starch-rods are still present in the yellow 
and fallen leaves of such of these plants as have been 
examined, viz. Euphorbia pulcherrima , E. Bojeri , E. Rothiana , 
Pedilanthus tithymaloides , Hura crepitans , Excoecaria bicolor , 
Sapium biglandulosum ; and appear to be here as numerous 
as in the mature green leaves. Since my return to England 
I have investigated the dead and withered leaves of Euphorbia 
Lathyris and E. graeca , and find the starch-rods quite 
evident in them. 
It looks then as if it is a general rule for the starch to 
be left in the laticiferous tubes of the dying leaves. On this 
account, as well as from the fact that these starch-rods are 
well formed in leaves not yet mature, it appears as if they 
are produced once for all in the tubes as these differentiate, 
and exist throughout the life of the organ, having nothing 
directly to do with carbon-assimilation. 
It is worth mentioning here that starch often remains in 
the guard-cells of the stomata as well as in the laticiferous 
tubes of dead leaves, whereas the rest of the leaf-tissue is, 
as a rule, free of starch : hence it might be argued that, as no 
doubt the starch is used by the guard-cells and reformed 
again and again, the starch of the laticiferous tube is also 
used and reformed again. This of course may possibly be 
the case. The point to emphasize, however, is that the 
starch seems to have no direct connexion with assimilation, 
and that the tubes can hardly be considered as starch con¬ 
ductors or storers. If it has any nutritive value, then it is 
for the use of the tubes themselves. 
1 Groom, Annals of Botany, iii, 1889. 
