IV. On the continuity of tho protoplasm tlirough the walls of vegetable cells. 87 
(sieve-plates, pits) and in others the whole cell-wall is perforated, consti- 
tuting one large sieve-slrueture. 
The physiological significance of such communication between adjacent 
cells appears to me not to be the same, in all cases. I am led to the con- 
clusion that the sieve-structures of endosperm cells like those of sieve-tubes 
serve as channels for the passage of food material, and are probably of equal 
importance during germination in connection with the transference of un- 
organised lerments, while as regards the filaments in such tissues as pulvini, 
their chief significance is that by their means the protoplasm of isolated cells 
beeomes connected and that thus the communication of impulses from one 
part of the plant to another is insured. For instanee there can be little 
doubt that the conduction of a Stimulus, which can be readily observed in 
the leaves of Minwsa pudica is effected by this means. 
The presence of these very minute perforations in the cell-wall need 
not lead to any modifieation of the generally accepted ideas as to the rnecha- 
nics of the cell, more particularly with regard to the maintainance of its 
turgid condition. 1t must be borne in mind that the lurgidity of a cell depends 
upon its protoplasm, and so long as this forms a perfectly closed sac, the cell 
can be turgid. In the case before us, the protoplasm does constilute a closed 
sac, for the filaments by which the protoplasmic bodies of neighbouring cells 
are connected, are solid. 
In conclusion it only remains for me to perform the pleasant duty of 
thanking those who have given me their help during this investigation, and 
first 1 v\ ould acknowledge the debt of gratitude that I owe to Professor Sachs 
for his uniform kindness and consideration to me during the time I was 
working in his laboratorv. The fad that it was at his Suggestion that I com- 
menced this work will alone be suffieient to show how great that debt is. 
From my friend and teacher Dr. S. H. Vijjes I have received constant assist- 
ance and advice all through this most difficult investigation. To my friend 
Dr. D. H. Scott I am also indebted for much valuable aid and criticism. 
