320 INTRODUCTION TO CETPTOGAMIC BOTANY. 



hence arises that enormous dusty mass of spores which a single 

 individual is capable of producing. They affect every part of 

 the plant v?hich is sufficiently succulent to admit of the jjene- 

 tration of their mycelium. Not only the leaves and stems, 

 but the flowers themselves, the stamens, anthers, and the ia- 

 most recesses of the seed, are ia turn affected. There are two 

 principal groups, those in which the spores are disposed inde- 

 finitely, and those in which they form distinct sori, covered 

 merely by the cuticle, or contained in a distinct cellular 

 envelope. Those species which infest the sexual apparatus 

 seldom attack the leaves or other organs ; but this is not uni- 

 versally the case, for bunt, which seems peculiarly attached to 

 the seed, occurs also upon the stem and leaves ; and this is the 

 ease, too, with the maize-smut. The principal colour of the 

 smutty Fungi, which constitute the first group, is black or 

 brown, and shades verging on black, but other colours also 

 occur, as red, lilac, and violet. In one fine Himalayan 

 species, on a Polygonum,, the bractes are expanded, and 

 assume the appearance of inflorescence ; but in general the 

 effect is to distort and disfigure the plants on which they grow, 

 sometimes destroying the texture altogether, and sometimes 

 leaving only a few of the harder vascular bundles, as in a 

 species which affects Gahnia and other allied plants in India 

 and New Zealand, or, indeed, our own U. olivacea on Carices. 

 In Tilletia the epispore is remarkable for being reticulated, 

 and while in Thecaphora the spores are aggregated or com- 

 pound, it is possible that in Polycystis the external vesicles 

 may be mere growths of the epispore. The germination of 

 several species has been observed, and the first effect is like 

 that of other Fungi ; but ia many species, as in ColeosporiuTn 

 (Fig. 6, b), and much more in the species of the next group, 

 the spores germinate at definite points, very much after the 

 fashion of pollen-gTains. The sprouting thread is a continua- 

 tion of the secondary membrane, as is very evident in Tilletia 

 (Fig. 72, b), from the different character of the external mem- 

 brane. In fact, in its first stage, it is precisely that of a fern. 

 The spores, however, after all, notwithstanding their analogy, 

 are not immediate means of propagation ; they are, in fact. 



