304 



NINETEENTH REPORT. 



NaCl i.s .00601. The humidity is said to remain constant no matter how 

 much the temperature may vary. 



NaCl solutions of various concentrations were placed in dishes 5 cm. 

 in diameter and 4 cm. deep (with the cover on). One-tentli of 1 cc. of a 

 sterile distilled water spore suspension was dropped on the under side 

 of the cover, and then dried in vacuo over CaCL. The cover was then 

 placed over the dish of salt solution and sealed with vaseline, the distance 

 between the surface of the solution and the dried spores being 2 cm. 

 The dishes were kept in an incubator at 25 C. in order to prevent con- 

 densation of water ujjon the spore bearing surface, such as might take 

 place with fluctuations in temperature. Examinations were made from 

 time to time under the low power of the microscope, germination being 

 thus readily observed. The following table gives the results of three sets 

 of experiments : 



Table 9. 

 Humidity Requirement for Germination of Spores. 



a Only a few spores germinated. Probably accidental. 



From the above results it is evident that the minimum amount of mois- 

 ture required for germination lies between 92.8 and 93.4% of saturation, 

 and that the time required for germination varies inversely as the per- 

 centage of humidity \ 



The spores germinating in tiie more humid air appears to be hygro- 

 scopic, judging from the thin enveloping ring of water visible under the 

 microscope. The germ tubes were also hydrotropic, projecting out into 

 the moist air rather than adhering to the surface of the glass as in the 

 ease when they are germinated in a hanging drop. 



»The results obtained by Lesage for /'. <jl<iiirinii are of interest for the sake of compari- 

 son. It is evident that tliis common mohl h;is a humidity requirement far below that of 

 M. sitrcinae forme. 



Showing interval in days elapsing before germination when spores of renicillium are kept 

 in moist chambers over various solutions of sodium chloride. 



Quoted from Davenport (1908). Experimental Morphology, p. 351. 



