Hydration and Growth of Colloids and Cell-masses. 



Ill 



water is modified, being generally accelerated by a rise within the range 

 of ordinary temperatures at which plants grow. Next, adsorption is 

 affected in a contrary manner, but the complex series of reactions 

 associated with respiration are speeded up, with consequences far too 

 complex to be characterized here. The first step, that of absorption 

 and diffusion, would be far simpler, as the rate of acceleration here 

 would be nearly identical with that of the diffusion of the same material 

 in water. 



A determination of the effect which temperature might have on 

 growth necessarily takes into account, first, the fundamental increase 

 which might accrue from simple absorption under various conditions. 

 In recognition of this fact, it was arranged to carry on swellings of 

 some of the biocoUoids in order to gain some appreciation of the im- 

 bibition factor in growth. Sections 0.2 mm. in thickness of plates of 

 agar 90 parts, bean protein 10 parts, and culture salts 0.85 per cent 

 were swelled at 15° C. and at 22° C. The rate of swelling may be 

 appreciated by a consideration of the total amounts at the end of 4 

 hours, 8 hours, and at the end of the test (fig. 19). 



4 p.m. 



p.m 



>2p.in. 



FiQ. 19. — Tracing of auxographic record of swelling of dried plates 0.2 mm. in thickness of a 

 salted "biocoUoid" consisting of 9 parts of agar, 1 part bean protein, and 0.015 part 

 nutritive salts. Increase is denoted by downward movement of the pen, amplified 20 times. 

 The initial rate and continuance of the swelling at various temperatures may be compared. 



Table 86. — Swelling of mixture of agar, bean protein, and cultures in distilled water. 



The hydration during the first 4 hours includes any process of 

 chemical union of water with the colloidal material by which water 

 in definite proportions enters into the molecular aggregates. The 

 greater part of this action probably takes place within the first half 



