DEPARTMENT OF BOTANICAL RESEARCH. 69 



the intine remaining intact. The degree of dispersion must be different 

 in the contrasted cases, and it is not impossible that such differences 

 are analogous to those expressing changes of permeability. 



The result of coagulation by one reagent is different from that caused 

 by another. When the cytoplasm is irreversibly coagulated by formic 

 acid, the gel, after drying, will swell less in aimnonia than in formic acid. 

 The coagulum formed in the presence of ammonia, which may be due 

 to the pressure exerted by the envelopes on the swelling colloids, has 

 a much softer consistency than that caused by acids. A coagulum is 

 formed without more swelling than just sufficient to stretch the enve- 

 lopes in very strong glycerine in the course of a few hours, and its con- 

 sistency is again different from that caused by alkah. This coagulum 

 will at once swell further and escape as a whole on the addition of 

 ammonia, the volume of the coagulum being much greater than if 

 caused by formic acid. Coagulation caused by acids takes place sud- 

 denly at certain concentrations of the reagent. It is alwa3's preceded 

 by swelling, but this swelling is due probably to the lower initial con- 

 centrations which first reach the protoplasm. 



The concentrations of acids and the consequent amount of swelling 

 and the forms assumed by the coagula are so various as to prompt 

 inquiry into the nature of their structure. One factor appears to 

 be the resistance offered by the superficial layer of coagulum to further 

 penetration of the reagent — this layer becoming a semi-permeable 

 one. It would seem that the specific actions of acids on protoplasm 

 may be due in part to coagulation eft'ects imposed upon hydratation, 

 and this possibihty is not confined to acids, since there is some 

 evidence that alkalis may also have a coagulative effect at certain 

 concentrations in addition to the power to cause swelling. Whether 

 the ammonia is the immediate cause or not, it is certain that the pro- 

 toplasm of pollen can be caused to coagulate in its presence, and 

 similarly in the presence of potassium hydrate (jV to f/N). Such 

 behavior seems to be quite different from that of gelatine and similar 

 colloids, so far as at present understood. 



The evidence upon which the above is based supports the view that 

 protoplasm is fundamentally a hydrophile emulsion colloid, of whose 

 momentary interrelations of disperse-phase and disperse-medium its 

 permeability is a function. The relation may be changed from moment 

 to moment by hydratations and coagulations which, if irreversible, 

 lead to death. 



Chemical Changes accompanying Desiccation and Partial Starvation of 

 Succulents, by E. R. Long, 



The attempt to obtain individuals which would illustrate the meta- 

 bolic changes taking place at intermediate stages of desiccation of 

 succulents was begun in June 1914, when six healthy ecliinocacti were 



