VARIOUS OBSERVATIONS 75 



The Monstrous Fruit-bodies of Polyporus rufescens. Polyporus 

 rufescens, of which some normal fruit-bodies are shown in Fig. 24, 

 is remarkable in that it sometimes produces large, more or less 

 spherical, monstrous fruit-bodies, like those shown in Fig. 23. 1 

 Mr. Burtt Leeper has informed me that near Salem, in the State of 

 Ohio, while normal and monstrous fruit-bodies are found together, 

 he has seen several hundred monstrous fruit-bodies about a stump 

 without a single fully developed one, and that he has also seen 

 several normal fruit-bodies in a group without the admixture of a 

 single monstrous one. 



It may be asked : how is it that Polyporus rufescens sometimes 

 gives rise to normal fruit-bodies and sometimes to monstrous ones ? 

 The answer to this question is to be found, perhaps, in the response 

 or non-response of the fruit-bodies to the morphogenic stimulus of 

 gravity. The form of a normal fruit-body is largely controlled by 

 gravity. The stipe is negatively geotropic, the pileus diageotropic, 

 the hymenial tubes positively geotropic ; and the dorsiventrality of 

 the pileus, including the development of the hymenial tubes on the 

 under surface, and not on the upper, is in all probability here, as 

 in other Polypori, decided by a morphogenic stimulus of gravity. 

 The stimulus of gravity, possibly, may influence the development 

 of a fruit-body in further even more subtle ways than any we have 

 yet perceived. Let us now imagine a fruit-body which, for some 

 reason or other, has lost its power of responding to the various 

 stimuli of gravity during its development. Then, surely, the fruit- 

 body could become nothing other than monstrous. In the absence 

 of control by external stimuli, it would certainly take on an unusual 

 form. Perhaps, on enlarging, it would grow centrifugally and thus 

 develop into a more or less spherical ball, and its hymenial tubes 

 might come into existence irregularly all over its surface or mixed 

 up with the fruit-body flesh, in the manner shown in Fig. 23. 

 I am therefore inclined to think that the monstrous fruit-bodies 

 of Polyporus rufescens owe their peculiar form to the loss of their 



1 Polyporus abortivus Peck appears to be a synonym for P. rufescens Fr. Peck 

 (Bot. Gaz., vi, 1881, p. 274) noticed the monstrous fruit-bodies and called them 

 P. abortivus var. subglobosus. Of this variety he says : " Plant consisting of a 

 depressed or subglobose mass, having the stem very short or obsolete, the central 

 substance marked by concentric zones and the surface everywhere porous." 



