§ 1] EFFECT OF DENSITY UPON KATE OF GROWTH 363 



Also Raciboeski ('96) found that Basidiobolus cultivated 

 in a nutritive solution containing 10% peptone, Ifo glucose, 

 and the necessary salts, ceased to grow when the concentration 

 of the salts reached the following percents : — 



sodium chloride, NaCl, 6%. glycerine, CaHjOj, 20%. 



potassium chloride, KNOg, 11%. glucose, CsHijOs, 25%. 



The foregoing maximum concentrations vary with the molec- 

 ular weights of the dissolved substances, indicating that their 

 effect is purely an osmotic one. 



Germination is likewise affected by concentration, as a valu- 

 able series of experiments by Vandevelde ('97) clearly shows. 



Seeds of the pea, Pisum sativum, were soaked for 24 hours in solutions 

 of common salt varying from 1% to 35%, then removed, planted, and the 

 percentage of seeds which germinated (G%) and the mean interval elapsing 

 before germination (I) determined. (I) was, more precisely, the time elaps- 

 ing (in days) before one half of the seeds had germinated. The results are 

 given as follows : — 



TABLE XXXVIII 



Showing the Relation between the Concentration of the Solution in 

 WHICH Peas have beeh soaked and their Germination 



This table yields some remarkable results. As the concen- 

 tration increases from 1% to 15%, the percentage of germina- 

 tions diminishes from 98 to 4.5, and the mean germination 

 interval increases from 2.1 days to nearly 7, near which point 

 it remains at all higher concentrations. From 15% to 29% the 

 percentage of germinations fluctuates so irregularly between 

 6.8 and 0.83 that within these limits it may be considered con- 



