INTRODUCTION TO CRYPTOGAMIC BOTAMY. 369 



genera have arisen in a similar way from the various forms of 

 fruit produced in different species, some of which are un- 

 doubtedly representatives of sexual distinctions, and some 

 possibly endowed with capability of impregnation. The differ- 

 ent terms conidia, stylospores, and spermatia, must at present 

 be regarded as more or less indefinite and xmcertain. But 

 apart from these circumstances, Fungi undergo great changes 

 in form and habit, so as to make their study very difficult.* 



405. The spores and sporidia afford good characters, pro- 

 vided so much stress is not laid upon particular appearances, 

 as to lead us to pronounce species different when the fruit is 

 merely in a different stage of development. The same species 

 may at different times have simple, uniseptate, or multiseptate 

 fruit, and its form will vary in different asci of the same indi- 

 vidual, though some general characters may be exhibited 

 by all. The size, again, varies very greatly, so that the 

 nicest microscopical measurement can be taken only as an 

 approximation. In Xylaria pedunculata, for instance, I 

 have seen highly nourished individuals produce sporidia at 

 least twice as long, with proportionate breadth, as in the normal 

 plant. The same species also, as observed above, gives an ex- 

 ample of the reduction of a large stipitate species with a scle- 

 rotioid rooting base, to a single, almost naked, perithecium. 

 It has been shown, too, that the ostiola of the perithecia are 

 equally variable in length. 



406. The spores of the sporophorous Fungi vary in a similar 

 manner. In the genus Hymenogaster, where the characters 

 depend mainly on the spores, it is scarcely possible to separate 

 many species with certainty, on account of the extreme varia- 

 tions assumed in different specimens, both as regards form and 

 sculpture. But if various forms are assumed by the fruit, 

 much more is this the case with the receptacle. The same 

 species, according to varying circumstances of position, mois- 

 ture, temperature, and other accidents, may be perfectly sessile, 

 seated on a distinct stem, with an orbicular pileus, or this 



*See, for further illustration of the duality of Fungi, Tulasne, in 

 Ann. d. Sc. Nat., s6r. 4, vol. 5, p. 108, publislied while this sheet was 

 under proof. 

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