HELIOTROPISM OF THE STIPE 125 



that the same is true for Coprinus comatus. Experiment alone can 

 decide this matter and definitely prove whether I was in error or 

 not. By experiment I was unable to detect any heliotropism for 

 the fruit-bodies of Psalliota campestris, the Common Mushroom ; 

 but in this species the stipes are relatively short and stout. How- 

 ever, Miss Streeter, in a paper on the influence of gravity on the 

 direction of growth of Amanita, has shown that the stipes of both 

 Amanita phalloides Fr. and of A. crenulata Pk., which are relatively 

 long and thin, are slightly heliotropic.^ Indeed, her results for 

 these two species exactly resemble my own for Coprinus sterquilinus, 

 for she found that with unilateral illumination the stipes of the 

 Amanitae become deflected toward the light so that they make an 

 angle with the vertical of from 8° to 12°. From her observations 

 and from my own upon Coprinus sterquilinus it seems highly probable 

 that it will be found that a shght amount of positive heliotropism 

 is characteristic of a great many, perhaps of the majority, of the 

 larger Agaricineae. So far as the smaller Agaricineae are con- 

 cerned, it will be remembered that, in the first volume of this work, 

 in respect to small Coprini, e.g. C. niveus and C. curtus (there called 

 C. plicatiloides), I pointed out : (1) that the stipe is at first ageo- 

 tropic but strongly positively heUotropic, so that until it is haK- 

 grown in length its axis is maintained in a direction coinciding with 

 the direction of the incident rays of light ; and (2) that, just before 

 the expansion of the pileus, and only then, the stipe undergoes a 

 remarkable change in its physiological state ; it becomes strongly 

 negatively geotropic and anheUotropic.^ For smaller fruit-bodies, 

 hke those of the smaller Coprini, this kind of reaction is without any 

 serious mechanical disadvantages, for the weight of the fruit-bodies 

 is small and the centre of gravity not far away from the base of the 

 stipe, in consequence of which there is no danger of the curved stipes 

 becoming broken or displaced by the weight of themselves and 

 their pilei.^ If the stipes of the relatively gigantic fruit-bodies 



1 S. G. Streeter, " The Influence of Gravity on the Direction of Growth of 

 Amanita," Botanical Gazette, vol. 48, 1909, p. 415. 



^ These Researches, vol. i, pp. 67-69. 



^ The ecological advantage in the successive reactions of the stipes to light and 

 gravity is that these reactions enable small fruit-bodies to emerge safely from between 

 the dung-balls. Ibid. 



