160 Groom. — On the Functions 
of distribution of the tubes would be of equal significance were 
the tubes excretory organs, or nerves influencing the meta- 
bolism of the cells. Further, the argument to be drawn from 
the apparent correlation between the development of the 
system of tubes and that of the conducting nerve-parenchyma, 
is inconclusive, inasmuch as the nerve-parenchyma is not 
exclusively concerned in the conduction of carbohydrates. 
The nerve-parenchyma stores tannin, alkaloids, salts, etc. ; 
hence the apparent correlation might have reference to one 
or other of these functions, and not at all to the conduction of 
carbohydrates. In fact, Van Tieghem uses this argument in 
support of his view that the laticiferous tubes are excretory in 
function. And I find that, as might be expected, the con- 
ducting parenchyma and the laticiferous tubes may both be 
well developed in the same leaf. 
Schimper’s observations on Euphorbia are at variance 
with those of Haberlandt. He found that the tubes are 
extensively distributed beneath the epidermis, and that they 
nearly always end there. By darkening leaves, he ob- 
served the mode of conduction of the carbohydrates. He 
showed thus that there is no reason for believing that the 
tubes take any share in this conduction. 
The present observations were undertaken for the purpose 
of determining the distribution and mode of ending of the 
laticiferous tubes in leaves. The mode of conduction of car- 
bohydrates was also observed, in order to decide if the tubes 
do assist in the process. 
Whole leaves or tangential sections were observed in chloral- 
hydrate. In addition transverse sections were made. These 
latter are not so satisfactory for the purpose because of the 
irregular course of the tubes. Haberlandt, Pirotta, and 
Marcatili seem to have judged chiefly from transverse sections. 
I found that Haberlandt 3 s statements were exaggerated. 
To see the mode of conduction of the starch either entire 
plants or attached leaves were darkened. The leaves were 
subsequently examined after treatment with a solution of 
iodine in chloral-hydrate. 
