Chapter X —161— Drosera 



cated in the behavior of various substances. It seems sure, however, 

 that some substances have only the property B, such as meat extract, 

 pepsin, peptone Witte, none of which can procure aggregation in empty 

 cells, that is cells devoid of A. But substances having A only seem 

 not to occur. On the other hand some substances can cause aggre- 

 gation in both normal and ''empty" cells, e.g., saliva, gland extract, 

 etc., and these, therefore, seem to have both properties A and B. 

 If this were true, we would be helped in understanding why aggrega- 

 tion can be procured by merely mechanical stimulation by assuming 

 that a substance containing AB is secreted only on stimulation, then 

 to diffuse into the stalk cells. To this it can be objected that the 

 cells of tentacle stalks with the glands removed can respond to pepsin 

 alone, indicating that B is already present in the stalk cells. 



But more, for it appears that tentacles are to be found in a state 

 of aggregation when they have never been stimulated in any way so 

 far as this can be ruled out by conditions of culture, as Homes 

 subsequently showed. The hypothetical substance we are looking 

 for must therefore inhere and have both properties A and B. Since, if 

 this is to be assumed to be the case, aggregation may not be present 

 till stimulation occurs, it must be argued that stimulation merely ac- 

 tivates B. 



Thus Miss CoELiNGH brings her argument into a purely theoretical 

 atmosphere which she, herself, finds hard to breathe, and says that 

 speculation without further experimentation affords no sure guidance. 

 But it must be evident that the problem of aggregation is most in- 

 triguing. 



To the previously cited results of Schimper, Gardiner, de Vries, 

 Akerman, in which they clearly distinguished between true aggregation 

 and Goebel's granulation, Erna Janson took a diametrically opposite 

 position, stating that all aggregation is due to the precipitation of mate- 

 rials in solution in the cell sap. Neither the tonoplast (de Vries) nor the 

 swelHng of the protoplasm have any part in the process. It does not 

 appear in her paper, however, that she has taken sufficient cognisance of 

 that condition called by de Vries " true " aggregation. Her figures, which 

 are very crude, give no hint that she brought this into her field of con- 

 sideration. She showed, what Bokorny also had shown at length, 

 that certain reagents (alkaloids, other weak bases) procure precipita- 

 tions in the vacuoles. Beyond this she failed to show that "true 

 aggregation" could thus be achieved. Nor did Bokorny's figure of 

 aggregation in Drosera show more. Considered as contributions to 

 the nature of the vacuolar contents, these papers have value. As 

 furnishing enlightenment on the nature of that kind of aggregation 

 which follows on mechanical stimulation and on feeding with pepsin, 

 peptone, etc. (though in these was suspected the presence of ammonia), 

 the work of Janson is very limited. For it is quite certain, and I 

 speak now from my own observations, that during true aggregation 

 there is no slightest evidence of precipitation from beginning to end. 



Following the studies of Darwin and Gardiner on aggregation a 

 new phase of the subject was entered upon, in which the cytological 

 changes taking place within the cells of the gland especially were ex- 

 amined. Lily Huie examined the behavior of the nucleus during se- 



