Certain Reactions of Biocolloids and Cell-masses. 75 



water which had fallen on a slate roof and collected in a closed cement 

 cistern gave a swelUng of 1,500 per cent. The water from the system 

 supplying the Desert Laboratory, taken from a well 40 feet in depth 

 in the alluvium of the flats along the Santa Cruz River and pumped 

 through an iron pipe line 6,000 feet long to a cement tank, produced a 

 swelling of only 800 per cent. As a final test, a soil solution was used 

 which was obtained by shaking up 600 grams of surface soil with 1,200 

 c.c. of distilled water and then allowed to stand for 12 hours. The 

 filtered solution applied to sections in the same manner as the other 

 waters induced a hydration of 900 per cent. (Fig. 10). 



These measurements afford a standard of desirabiUty of the water 

 from these various sources for cultural work and for drinking purposes. 

 Since growth consists in the main of the hydration of plasmatic col- 

 loids, the nutritive solution most favorable to this process would be an 

 important factor in an environmental optimum. It was also possible 

 to make tests of these natural waters with a biocoUoid which included 

 6 parts agar, 2 parts prosopis gum, 1 part gelatine, and 1 part bean 

 protein, to which had been added 0.2 per cent of culture solution. 

 Such a mixture, like one containing gum arable, shows high swelling 

 in acids and less in salts, whether acid or alkaline. Swelling of plates 

 0. 17 mm. in thickness were as shown herewith :' 



Table 67. 



p. ct. 



DistiUed water (25° C.) 1,760 



Rain water (27° C.) 1,794 



WeU water (27° C.) 1,706 



SoU water (25° C.) 1,500 



The higher temperatures at which the swelUngs in rain water and 

 well water were made prevents direct comparison, but it may be sup- 

 posed that a biocolloid already charged with salts to a point above the 

 average of land plants would be hydrated in the dilute solution 

 offered by the cistern water practically as readily as from distilled 

 water. The figure given expresses the increase at a temperature 2° C. 

 higher. The same would be true of the well water as compared with 

 the soil solution. It is to be noted that the difference between the 

 reaction in the solutions and in pure water is less than in the unsalted 

 colloid. Of course, the substitution of prosopis gum for opuntia 

 mucilage is also a factor. Relations to environmental conditions of 

 some importance are suggested. The- reactions of the halophytes 

 should include some effects similar, in that there would be offered 

 the phenomena of the swellmg of cell-masses high in salts (fig. 10). 



Some experiments in the modification of germ-plasm in 1905 resulted 

 in the formation of embryos developing into individuals not entirely 

 identical with the parental types. The essential feature of the experi- 

 ment consisted in the successful introduction of various substances 

 into the neighborhood of the embryo-sacs at the time that fertilization 



