PANUS STYPTICUS 



361 



f^iyf^' 



spores falling from the three upper fruit-bodies before they would 

 have time to settle on the tops of the pilei below. The manner in 

 which the spores are carried away from the pilei by the wind is 

 illustrated diagrammatically in Fig. 161. 



The divergence of caespitose or much crowded fruit-bodies is a 

 phenomenon not peculiar to Panus stypticus, but one which may 

 be observed in Polyporus sqtiamosus, Lentinus lepideus, and many 

 other Hymenomycetes.^ Its exact causes 

 require elucidation. In the three species 

 just named the divergence seems to be 

 due, firstly, to the fact that the stroma 

 upon which the fruit-bodies arise bulges 

 out more or less hemispherically from the 

 substratum and, secondly, to the fact that 

 the stipes of the individual fruit-bodies, 

 which when very young are ageotropic, 

 grow out in a direction which is perpen- 

 dicular to the surface of the stroma. The 

 more or less horizontal position taken up 

 by the pilei, when these come to be de- 

 veloped, is doubtless due to geotropic 

 stimuli. The divergence of the fruit- 

 bodies in clusters of Coprinus micaceus. 

 Armillaria melha, and Pleurotus ostreatus, 

 etc., growing naturally in the open, and of 

 Psalliota campestris growing in beds of manure may be due to 

 mechanical pressure alone or, possibly, to a reaction to mutual 

 contact stimuli. From the functional point of view the phenomenon 

 of fruit-body divergence, wherever it occurs and however it is 

 caused, is of high importance, for it is a prime factor in providing 

 those spaces between adjacent fruit-bodies ^^hich are required to 

 enable the wind to carry away the spores and thus bring about the 

 dissemination of the species. 



Retention of Vitality after Desiccation and during Frost.— 

 During moist weather the pilei of Panus stypticvs are flattened and 



^ Cf. these Researches, vol. i ; for Poli/porus squainosKs, p. 57, also Plate V, 

 Figs. 31, 32, 36 ; for Lentinus lepideus, p. 48, also Fig. 16, A. 



Fig. IGl. — Panus stypticus p.f. 

 lumitiescens. Vertical sec- 

 tion through four fruit- 

 bodies forming an imbri- 

 cating cluster attached 

 laterally to a tree. To 

 show the divergence of the 

 fruit-bodies from one an- 

 other and the spore-clouds 

 being carried away by the 

 wind. Obtained at Mont- 

 real, Province of Quebec, 

 Canada. Natural size. 



