348 RESEARCHES ON FUNGI 



I placed a board of coniferous wood, upon which some S. stellatus 

 fruit-bodies were developing, flat upon the floor of a large cubical 

 glass case which was situated on a table next to a wall and about 

 21 feet distant from each of two windows. About twelve fruit- 

 bodies developed on the horizontal upper side of the board and, 

 during their growth to maturity, which was completed in the course 

 of two or three weeks, they were unilaterally illuminated each day 

 by daylight coming from the two windows (Fig. 165). Under 

 these conditions the fruit-bodies did not project straight upwards 

 from the board but, at an early stage in their growth, inclined them- 

 selves toward the direction of the greatest illumination so that the 

 longitudinal axis of each of them came to make an angle of some- 

 what less than 45° with the upper surface of the board. The result 

 of the fruit-bodies having their apices turned toward the light in 

 this way was that, when the fruit-bodies came to discharge their 

 glebae, the glebae hit and stuck to the side of the glass case which 

 was nearest the windows, i.e. nearest the source of the brightest 

 light. 



Miss Walker, 1 in treating of the relations of Sphaerobolus with 

 light, says : " Buller in unpublished work previously mentioned 

 showed a positive heliotropic reaction, and experiments conducted 

 by the writer entirely confirm his results. That fruit-bodies in 

 flask cultures point in various directions is due to reflections and 

 refractions of light in the culture flask. When cultures were placed 

 several feet from a window and arranged so that no reflections of 

 light were possible, all basidiocarps formed pointed directly toward 

 the source of the light." 



Both Miss Walker 2 and I have observed that the directive 

 action of light on Sphaerobolus is limited to very, young fruit- 

 bodies and does not affect fruit-bodies which are maturing. At 

 present, we do not know how light causes a Sphaerobolus fruit-body 

 to develop so that its apex faces the incident rays, and it is possible 

 that Miss Walker's assumption that the phenomenon is one of 

 heliotropism may be incorrect. There are three theoretical 

 possibilities for the mode of action of the light. Light may influence 



1 L. B. Walker, 1927, loc. cit., p. 159. 



2 Ibid, 



