420 



EFFECT OF LIGHT 



[Cn. XVII 



Fig. 1 



observers in the early half of the century, and, more recently, 

 NOBBB ('82), ADRIANOWSKY ('83), and others, have shown 

 that germination of seeds takes place slightly earlier in the 

 dark than in daylight. Among fungi, also, we have the assur- 

 ances of HOFFMANN ('60, p. 321) that the spores of the mush- 

 room Agaricus campestris germinate more slowly in the light ; 

 and of DE BARY ('63, p. 40) that the spores of the potato 

 fungus, Peronospora infestans, and its allies do germinate with 

 difficulty in the daylight, and not at all in the sunlight. Thus 



the germination of spores 

 even more than of seeds is 

 retarded by light (p. 174). 



Passing now to the growth 

 of fungi, we find numerous 

 and harmonious observations 

 on the effect of light. FRIES 

 ('21, p. 502) first noticed 

 that the growth of fungi is 

 retarded in the light, and 

 ScHMiTz('43, p. 51 2), KRAUS 

 ('76, p. 6), VINES ('78), STA- 

 MEROFF ('97), and others 

 have confirmed this result 

 for hymenomycetes, the er- 

 got fungus, and molds.* 

 BREFELD ('77, p. 90 ; '89, 

 p. 275) found that the toad- 

 stool Coprinus stercorarius 

 reared in the dark attains a 

 length of two feet or more, 

 while in the daylight it is 

 only an inch long (Fig. 119). 

 Again, the sporangiferous 

 hypha of the dung mold Pi- 

 lobolus microsporus, which 

 is eight or ten inches long 



5, roots; 6,hyphae. (From BREFELD, 77.) in the dark, grows only half 



FIG. 119. Coprinus stercorarius in reduced 

 size. Fig. 1, typical young fruiting 

 fungus reared in the light. Fig. 2, a, b, 

 c, d, fungus reared in weak illumination. 

 Fig. 5, Coprinus reared in darkness. 

 1, sclerotium ; 2, 6, stalk ; 3, 4, fruit ; 



* But BULLOT ('97) denies it in the case of Phycomyces nitens. His experi- 

 ments are not, however, convincing. 



