IX. TEMPERATURE AND THE HYDRATION AND GROWTH 

 OF COLLOIDS AND OF CELL-MASSES. 



Living material is a colloidal mass consisting of a mixture of 

 colloids, the most important components of which are carbohydrates 

 and proteins or protein derivatives. Salts of sodium, potassium, and 

 magnesium in various combinations are dissolved in the system. The 

 denser portions of the protoplasm, including all of the continuing 

 structures, or those of morphological rank, have the properties of an 

 elastic gel with the general structure of a fine sponge or a honeycomb 

 with irregularly broken or incomplete walls. The materials which 

 make up this fairly continuous structure are also in a disperse or liquid 

 condition in the cavities and may even fill large syneretic spaces in the 

 general structure. 



The essential feature of growth consists in the accretion of material 

 entering into this colloidal structure, its hydration, and its arrangement 

 into additional structures or portions of honeycomb. This may be 

 pictured as taking place by an initial increased dispersion or enlarge- 

 ment of the colloidal network to a point where new masses of gel would 

 be formed in the liquid phase of the existing mesh. Considering living 

 material as an intimate mixture of minute particles of its main colloidal 

 components (and the scanty evidence on this matter is to the effect 

 that the carbohydrates and proteins do not diffuse into each other), it 

 is on this basis to be assumed that the new material would accrue to 

 these separately and in a characteristic and differentiated manner. 



Aggregations of the introduced material might also take place in 

 syneretic cavities, with opportunity for the development of specialized 

 structures. The absorption and diffusion of material in liquid form 

 and its diffusion into the colloidal mass would in all cases be the initial 

 step in growth. The consequent swelling with all of its accompani- 

 ments and consequences in cell-masses of plants and in my biocoUoidal 

 mixtures has been found to depend upon the character and the pro- 

 portion of the proteins or protein derivatives in the colloid, the pro- 

 portion of the pentosans, and the amount of salts present. In addition 

 to these features, which change but slowly, the active metabolism of 

 the growing cell includes respiration in which substances such as sugars 

 may be adsorbed on surfaces of aggregates of enzymes which catalyze 

 them, acids occurring at certain stages of the resultant reactions. 

 Acidity in a growing cactus, for example, may vary between a value of 

 0.1 N malic acid and one-twentieth of this amount during the course 

 of a daylight period, causing very marked changes in the imbibition 

 and absorption of the cell-colloids. 



The exposure of a growing or swelling colloid to different tempera- 

 tures has several effects: First, the rate of absorption and diffusion of 



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