of Laticiferous Tithes, 163 
striking because the general parenchyma of the upper half of 
the leaf contained a considerable amount of starch. So, unless 
the conducting apparatus was disabled, it appears that it must 
have been overworked, and could not store or remove the 
starch sufficiently rapidly. Hence the assistance of any ac- 
cessory storing or conducting apparatus would have been very 
welcome. Much stress is not laid on these observations with 
isolated leaves, as the conditions were abnormal. Though, as 
far as the tubes are concerned, mere section does not have 
any serious affect, in some plants at any rate 1 . The latici- 
ferous tubes contained starch till the death of the plant. 
In Sapium sp. the laticiferous tubes contain rod-shaped 
starch-grains. Owing to the large size of the leaves, quanti- 
tative statements concerning the starch inside their tubes are 
not to be wholly trusted. However, there was no sign of di- 
minution of this starch in leaves darkened for forty-eight hours. 
The starch-grains of the general leaf-parenchyma were exces- 
sively minute in my material. In the darkened leaves starch 
could only be seen inside the tubes, in the nerve-parenchyma 
of fair-sized nerves, and in the guard-cells of the stomata. 
Hence the nerve-parenchyma had conducted the starch from 
the general leaf-parenchyma ; yet considerable quantities of 
starch remained in the peripheral subepidermal tubes. 
The Manihot-leaf is not eminently suited for the study of the 
question, because the free parts of the tubes are relatively 
short. 
Artocarpeae. 
The leaves of Pharmacosycea sp. are moderately thick. The 
upper epidermis is succeeded by a layer of aqueous tissue. 
Beneath this in turn come two layers of palisade-cells. In 
the spongy parenchyma the tubes, as a rule, simply cross from 
vascular bundle to vascular bundle, but sometimes they end 
in this layer. They then ascend to the palisade-layers in 
which they form a very complete system. Many of them 
1 See Schullerus and Faivre, loc. cit. 
