Chapter X — 147 — Drosera 



De Vries' studies were most illuminating. He examined cells of the 

 tentacle stalk. He says that the whole process of aggregation falls into 

 two periods. In the earlier period there is a pronounced increase in the 

 rate of cyclosis of the protoplasm, accompanied by growing complexity 

 of the currents (" differentiation"). Many accounts ignore this, 

 though Gardiner mentioned it. During the second period there is a 

 breaking up of the vacuole into a varying number of smaller ones, the 

 more obvious phase usually seen. These periods are not sharply de- 

 fined, the first passing over gradually into the second. 



The rapidly circulating protoplasm, with its breaking up into new 

 streams, furnishes a mechanism for subdividing the originally single 

 vacuole which in the meantime loses some of its sap. This escapes 

 through the wall of the vacuole (the " tonoplast") into the space be- 

 tween this and the protoplasm. This escaped sap retains its osmotic 

 pressure, since tentacles in aggregation are as rigid as otherwise. Left 

 behind, however, are the pigment, albuminoids and tannin which can 

 be precipitated within the resulting vacuoles. The vacuoles, however, 

 are now less rigid and more readily broken up by the cutting streams 

 of protoplasm. There result eventually many lesser vacuoles as drop- 

 lets of various shapes, especially slender tubular ones, constantly stirred 

 up by the moving protoplasm, and thus constantly changing positions. 

 De Vries attempts an interpretation of these changes by suggesting 

 that the heightened circulation of protoplasm may serve to facilitate 

 the movements of nutritive materials absorbed by the glands; that 

 the contraction of the vacuoles is connected with the partition of sub- 

 stances (acids, enzymes). 



Here it should be pointed out that the process of aggregation, 

 thought to be observed in stimulated tentacles, is quite independent of 

 the process of inflexion of the tentacles, as Darwin pointed out. I 

 myself have observed that the bending of the tentacles occurs in a 

 region where no aggregation had taken place. As pointed out by Jost 

 (Benecke-Jost, 1924) aggregation takes place in a primarily stimu- 

 lated tentacle downwards from cell to cell, but also later in those 

 tentacles secondarily stimulated, but does not in these precede the 

 bending movement, and moreover proceeds not from the base upwards 

 but from the gland downward. Aggregation can, therefore, have no 

 relation to the transmission of stimulus, likely enough as it first seemed. 



I have mentioned above that, on the escape of sap from the vac- 

 uoles, there is left behind a variety of substances, pigment, tannin, 

 albumin, which can be precipitated by various chemical agents (al- 

 kaloids, weak bases) and then appear as minute droplets or granula- 

 tions which coalesce into larger ones, and which in the case of tannin 

 and albumin can become brittle masses. Such precipitation was con- 

 fused by Darwin with true aggregation. Gardiner called this " pas- 

 sive aggregation," Goebel " granulation." Glauer (1S87) {fide F. 

 Darwin in Darwin, 1875) and Bokorny (1889) extended the dis- 

 tinction, the latter recognizing other kinds of aggregation to the num- 

 ber of four, viz.: the contraction of the entire protoplasmic utricle, 

 contraction and division of the vacuoles {'' true aggregation"), the 

 precipitation of albumin in the vacuoles and fourth, in the protoplasm. 



The albumin in question has been called " active albumin" by O. 



