274 RESEARCHES ON FUNGI 



Fig. 37. — Conical processes developing on a stromatous knob in the dark. 

 Natural size. 



Fig. 38. — Branched stag's-horn-like fruit-body produced from a conical 

 process. It was grown in the dark until it had nearly attained its full size. It 

 was then feebly illuminated with daylight. Whilst previously it had been quite 

 sterile, it reacted to the stimulus of light by developing on its underside three 

 white patches of hymenial tubes, j natural size. 



Fig. 39. — Part of the stag's-horn-like fruit-body just described shown in 

 natural size. The hymenial tubes look downwards. 



Fig. 40. — Two trumpet-shaped fruit-bodies developed from branches of a 

 stag's-horn-like structure grown in the dark. The two pilei began their develop- 

 ment unexpectedly. Since stag's-horn-like structures usually remain quite sterile 

 in the dark (cf. Fig. 20 in the text, p. 58), the development of these two pilei was 

 probably initiated by the light which was allowed to enter the dark-room each 

 day for the purposes of observation. About h natural size. The scale shows 

 3 inches. 



Fig. 41. — Some fruit-bodies were found growing on a log in the open. When 

 they were exceedingly rudimentary (at a stage slightly in advance of that shown 

 in Fig. 32), the log was taken into the dark-room and so placed that the fruit- 

 bodies were directed downwards obliquely at an angle of about 45° from the 

 vertical (c/. Fig. 42,/). The stipes on continuing development curved upwards 

 through an angle of more than 100° until the planes of the young pilei had been 

 brought into a horizontal position as here shown in the figure. This experiment 

 proves that fruit-bodies can take up normal positions in regard to the substratum 

 and assume fairly normal shapes in the absence of light. About i natural size. 



Fig. 42. — Thin sections taken through the median planes of various fruit- 

 bodies all photographed together. The white strips of paper show the positions 

 of the wood surfaces upon which the fruit-bodies grew : — 



a, very eccentric pileus — commonly found in nature ; 



b, less eccentric pileus — less commonly found in nature ; 



c, nearly centric pileus grown on the top of a stump (cf. text-figures 1, p. 8, and 



22, p. 61)— rarely found in nature ; 



d and e, sections through the two trumpet-shaped fruit-bodies shown and 

 described in Fig. 40. They were grown in the dark in the laboratory ; 



/, fruit-body started in light and then allowed to complete growth in darkness- 

 (cf. Fig. 41). The negative geotropic curvature of the stipe is marked,, 

 but the diageotropism of the pileus is not so pronounced as when 

 development takes place in the light ; 



9, very young trumpet-shaped fruit-body developing on a branch of a stag's- 

 horn-like structure after this had been exposed to light for an hour. 



