4 8 



Scientific Proceedings (87). 



What mechanism may be producing the positive findings in the 

 different cases, it is difficult to say. At any rate, various factors, 

 such as the constriction of the pupil in the case of opium, vaso- 

 motor changes produced by antipyretics, specific effect upon the 

 retinal ganglia and nerves and central cerebral effects must be all 

 considered. 



136 (1314) 



The relation of growth and swelling of plants and biocolloids to 



temperature. 



[From the Desert Laboratory, Tucson, Arizona.] 



By D. T. MacDougal. 



The varying constitution and resultant water-relations of the 

 plants may be simulated by mixtures consisting of agar and 

 albumen, or albuminous derivatives, or most successfully by 

 proteins extracted from beans or oats. 



The swelling of living and dried sections of plants and of 

 dried plates of such biocolloids in various solutions has been found 

 by the author to depend upon the history or previous treatment 

 of the material, the proportions of protein or albuminous deriva- 

 tives, and pentosans present, concentration of the solutions and 

 the temperature. 



According to Taylor heat should diminish imbibition in 

 gels, while cold and pressure will increase it. 1 The velocity 

 and swelling capacity of two biocolloids at temperatures within 

 the range of growth of plants used for comparison are illustrated 

 by the following auxographic measurements expressed in percent- 

 ages of increase of the original diameter of sections of dried plates: 



Swelling of Thin Plates of Agar, 90 Parts, Bean-protein 10 Parts and Nutri- 

 ent Salts .8 Part. 

 Increase in thickness in percentages of the original. 



Temp. 



Duration of Swelling. 



4 Hours. 



8 Hours. 



888% 



1,113% 



1,388 



1.550 



1,472 



1.735 



2,486.1 



2,736.0 



2,153 



2.347 



2,361 



2,514 



10-12 Hours. 



20-22 Hours. 



15-16 0 c 



21-23° C. 



30-31° C. 

 39° C... 

 46-47 0 C. 

 48-49° C. 



(12 hours) 2,791 

 (10 hours) 2,361 

 Complete 



1.325% 



1,900 



2,022 

 Complete 

 Complete 



1 Taylor, "The Chemistry of Colloids," p. 155, 1916. 



