356 



Profs. Percy Franldaiid and Marshall Ward. 



bring out clearly the retarding action of the light, especially on noting 

 that the temperature of the retarded culture was slightly higher, 

 rather than lower, than the other. 



Effects of Intense Insolation. 



Spores sown in a broth drop had germinated and developed good 

 filaments in the dark at 20 22 C. ; the culture was then put on a 

 cool slab over-nighfc, and kept slowly growing at 10 12 C. 



At 10 A.M. the twenty-four hours culture had fine strong filaments 

 when put at the south window under the l/12th immersion, with 

 Zeiss' screw micrometer eye-piece, for exact measurements of the 

 growths. Each division of the scale gave exactly 2 u. 



The segment selected was an isolated one measuring just 50 /t long, 

 and consisting of four distinct segments, each again, but less ob- 

 viously, divided by a median or nearly median septum into two cells. 



The diagrams below give the successive growths of these seg- 

 ments arid cells, as observed from 10.40 to 12.27 under the power 

 named, and fully bear out my previous observations that the growth 

 is not perfectly uniform over the filament. 



The following table summarises the total growth of the filament as 

 a whole. 



Curve 52. 



