40 FUNGI. 



other with great difficulty. As might be anticipated, this has 

 considerable effect on the contour of the spores, which in pul- 

 verulent species are shorter, broader, and more ovate than in 

 the compact species. If a section of one of 

 the more compact sori be made, it will be 

 seen that the majority of the spores are side 

 by side, nearly at the same level, their apices 

 forming the external surface of the sori, but 

 it will not be unusual to observe smaller 

 and younger spores pushing up from the 

 22.— Pseudospores hymenial cells, between the peduncles of 

 of Pucnnm. fo e e ],3 er gpores, leading to the inference 



that there is a succession of spores produced in the same pulvi- 

 nule. In Podisoma, a rather anomalous genus, the septate spores 

 are immersed in a gelatinous stratum, and some authors have 

 imagined that they have an affinity with the Tremellini, but 

 this affinity is more apparent than real. The phenomena of 

 germination, and their relations to Swstelia, if substantiated, 

 establish their claim to a position amongst the Pucciniceii* It 

 seems to us that Gymnosporangium does not differ generically 

 from Podisoma. In a recently-characterized species, Podisoma 

 Ullisii, the spores are bi-triseptate. This is, moreover, peculiar 

 from the great deficiency in the gelatinous element. In another 

 North American species, called Gymnosporangium biseptalum, 

 Ellis, which is distinctly gelatinous, there are similar biseptate 

 spores, but they are considerably broader and more obtuse. In 

 other described species they are uniseptate. 



Ustilaginei. — These fungi are now usually treated as distinct 

 from the Cceomacei, to which they are closely related.f They 

 are also parasitic on growing plants, but the spores are usually 

 black or sooty, and never yellow or orange ; on an average much 

 smaller than in the Cceomacei. In Tilletia, the spores are 

 spherical and reticulated, mixed with delicate threads, from 



* Cooke, "On Podisoma," in "Journal of Quekett Microscopical Club," vol. ii. 

 p. 255. 



t Tulasne, " M^moire sur les Ustilaginees," in " Ann. des Sci. Nat." (1847), 

 vii. pp. 12 and 73. 



