THE MORPHOGENIC EFFECT OF LIGHT 



113 



and physiological significance as the more highly developed and 

 much longer pseudorhizae of Collybia radicata and Coprinus macro- 

 rhizus which will be described in a subsequent volume. 



Fruit-bodies, whether grown in light or in darkness, complete 

 the construction of their solid stipe-bases first. They then rapidly 

 enlarge their pilei and subsequently elongate the main hollow 

 shafts of their stipes. A hollow shaft of a stipe will henceforth 

 be called a stipe-shaft. 



Whilst the stipe-base 

 of a fruit-body is develop- 

 ing, the pileus remains 



Fig. 64. — Coprinus sterquilinus. 

 Comparison of a fruit-body 

 grown in daylight with an 

 equal-aged fruit-body grown 

 in the dark ; to illustrate 

 the fact that light inhibits 

 the lengthening of the solid 

 stipe-base. A, grown in the 

 light ; C, grown in total dark- 

 ness. B and D, vertical 

 sections of A and C respec- 

 tively ; a, the solid stipe- 

 base ; b, the hollow stipe- 

 shaft. Culture medium, 

 sterilised horse-dung balls. 

 The fruit-body A soon 

 pushed up into the liglit 

 with the result that light 

 soon inhibited the growth 

 in length of its stipe-base, 

 which is therefore relatively 

 short. The fruit-body C, 

 having grown in the dark, 

 was not able to push up into 

 the light and therefore light 

 has not inhibited the growth 

 of its stipe-base which, in 

 consequence, has grown to 

 the maximum possible 

 length. In A and B, the 

 shortness of the stipe-base 

 is correlated with an ad- 

 vanced state of development 

 of the pileus ; in C and D, 

 the great length of the stipe- 

 base is correlated with a re- 

 latively very rudimentary 

 pileus. The pileus of A would 

 have expanded and begun 

 to shed spores about three 

 days before that of C. 

 Natural size. 



VOL. IV. 



