Guilliermond - Atkinson — 174 — Cytoplasm 



If one observes more closely the changes in appearance of the 

 vacuoles brought about by hydration and fusion of small vacuoles 

 into one large one, and, inversely, if one observes the fragmentation 

 into very numerous, small, semi-fluid, filamentous or reticulate vacu- 

 oles — a sort of splitting up of the large vacuoles — one is led to admit 

 that in these phenomena the vacuoles play only a passive role. 

 Their contraction and division are brought about by the degree of 

 water taken into the cytoplasm which causes movements of the 

 latter, the consequences being felt by the vacuoles. The cytoplasm, 

 under some influences, may extract a part of the water contained 

 in the vacuole and may swell. This swelling is therefore produced 

 by movements of the cytoplasm, particularly by emission into the 

 vacuoles of lamellate prolongations which finally partition off the 

 vacuole into multiple vacuoles. These, in losing their water, be- 

 come very viscous and look like chondriosomes. In the reverse 

 process, the cytoplasm is capable of restoring to the vacuoles a 

 part of their water of imbibition, bringing about a hydration and 

 increase in volume of the latter. These then fuse into a single 

 large vacuole. It is phenomena of this type which must take place 

 at the beginning of the maturation of the seed and which must 

 take place during the process of plasmolysis; some of the water 

 from the vacuole passes into the cytoplasm and must cause a swell- 

 ing, to which may be attributed the fragmentation of the vacuoles, 

 and it is not until later that the cytoplasm in turn gives up its 

 water to the exterior. In germination, the contrary phenomena 

 must take place. The vacuole absorbs the water at first accumu- 

 lated in the cytoplasm, and, as the latter continues to dehydrate, 

 the vacuoles progressively swell and again fuse to form a very 

 large vacuole. This view of the matter seems, moreover, to be 

 confirmed by the fact that the viscosity of the cytoplasm increases 

 as the plant grows old, correlative with the development of the 

 vacuole which ends by occupying almost the entire cell. 



This reversibility of vacuolar form is to be compared with a 

 remarkable phenomenon in the tentacles of the leaves of Drosera 

 rotundifolia, described long ago by Charles Darwin, and desig- 

 nated by him as aggregation. While studying the modifications 

 which occur in the pedicel of the tentacles as a result of the stimulus 

 produced by an insect, Darwin saw in each cell that the cytoplasm, 

 which was colored red by pigment before stimulation, broke up 

 before long into an aggregate of deeply stained corpuscles appear- 

 ing as granules, clubs, rods or filaments showing amoeboid move- 

 ments. The study of this phenomenon, taken up by various authors 

 (Gardiner, de Vries, Goebel, and akerman) has shown that in 

 reality the phenomenon observed by Darwin consists of a multiple 

 fragmentation of the vacuole and not of the cytoplasm. The cells 

 of the tentacle contain a single, very large vacuole filled with antho- 

 cyanin. At the moment of stimulation this vacuole undergoes a 

 great fragmentation. It splits into a large number of small chon- 

 driosome-shaped vacuoles. Immediately after stimulation, these 

 minute vacuoles fuse to constitute again a single large vacuole — 



