COLLOIDAL BEHAVIOR OF PLANT PROTOPLASM. 155 



day. After this the exag-geration slowly decreased and the retrac- 

 tion increased until the two balanced about the eighth day. The two 

 movements continued for a total period of 67 days. It is suggested 

 that the exaggerated swelling following a renewal of the solutions 

 may be due to the formation of glycocoll agarate, the bulk of which 

 might be greater than that of the agar. Diffusion of this material 

 from the section would result in a retraction or shrinkage. 



10. Plates of colloids cast on glass and prevented from shrink- 

 ing in area take on a heterotropic structure which varies in agar, 

 gelatine and in mixtures of the two. The swelling of an agar plate 

 is almost wholly in thickness so that the increase of a hydrated sec- 

 tion is denoted directly by the thickness reached. Gelatine plates 

 prepared in the same manner may increase as much as 60 per cent, 

 in length and width while swelling. Plates of mixtures of the two 

 swell from 6 to 16 per cent, in length and width, this amount being 

 modified by the character of the hydrating solution. These effects 

 which may play an important part in morphological procedure in the 

 cell, seem to indicate a meshwork structure of biocolloids as it does 

 not seem possible for emulsions to be differentiated in the manner 

 implied. 



Hydration Tests of Various Biocolloids. 



In the effort to ascertain the character of the biocolloids which 

 might show hydration reactions of the range and variety of proto- 

 plasm, empirical mixtures of agar and gelatine were made up and 

 cast into plates which were dried and then swelled under the auxo- 

 graph. Eight colloidal preparations were hydrated in water, hydro- 

 chloric acid, potassium hydroxide and glycocoll at 15° C. Trios of 

 sections were swelled under the auxograph in the usual manner, the 

 increases being calculated in percentages of original thickness by the 

 left hand number of each couple. Strips of the same material 50 

 to 80 mm. in length were placed in test tubes of' similar solutions. 

 The resulting increases ranged from 2 to 12 per cent, in length and 

 width in the different colloids. These ratios were applied to the 

 increases in thickness to obtain the total volumes expressed in the 

 right-hand number of each pair in Table I. 



