1 66 Groom. — On the Function 
Conclusions. 
1. The laticiferous tubes may be distributed throughout 
the whole of the leaf, and may end in contact with both the 
epidermis and the mesophyll. 
2. In some leaves the endings of the tubes are chiefly in 
contact with the epidermis ; in others again the endings are 
chiefly or exclusively away from the epidermis. 
3. The tubes may, in the leaves, desert the assimilating 
tissue altogether, as in the Artocarpeae where the tubes pass 
through the aqueous tissue to the epidermis. 
4. Thus there is no essential connection between the end- 
ings of the laticiferous tubes and any particular tissue of the 
leaf. Hence we gain no definite insight into the function of 
the tubes by observing their mode of ending. 
5. Observations on the conduction of carbohydrates in 
darkened leaves tend to show that the tubes do not conduct 
carbohydrates. 
It may be pointed out that this method of observing the 
transport of carbohydrates is not perfectly satisfactory. It is 
conceivable that carbohydrates might be removed by the tubes 
so rapidly as not to permit the formation of transitory starch 
in the adjoining cells; hence it would be extremely difficult 
to observe that the tubes assisted in this conduction. Another 
fact tells us that, if carbohydrates be conducted along the 
tubes, conduction must be rapid ; it is that carbohydrates are 
present in the latex in small quantities, in fact sometimes 
analysis fails to detect their presence at all. Here we see the 
value of the experiments on the euphorbiaceous leaves ; in 
them the movement of the starch is very slow, at any rate, 
when the leaves are darkened. In addition the complicated 
and tortuous course of the tubes does not suggest rapid con- 
duction. So altogether there is no reason for supposing that 
the tubes conduct carbohydrates. 
What then is the function of the starch inside the tubes ? 
It has been shown that it is improbable that the starch is a 
useless excretion. Yet when leaves or whole plants are 
darkened for a considerable period, starch remains in the tubes. 
