STRUCTURE. 41 



whence they spring. In the best known species, Tilletia caries, 

 they constitute the " bunt " of wheat. The peculiarities of 

 germination will be alluded to hereafter. In ITstilago, the 

 minute sooty spores are developed either on delicate threads 

 or in compacted cells, arising first from a sort of semi-gelati- 

 nous, grumous stroma. It is very difficult to detect any threads 

 associated with the spores. The species attack the flowers and 

 anthers of composite and polygonaceous plants, the leaves, 

 culms, and germen of grasses, &c., and are popularly known as 

 " smuts." In Urocystis and Thecaphora, the spores are united 

 together into sub-globose bodies, form- 

 ing a kind of compound spore. In 

 some species of Urocystis^ the union 

 which subsists between them is com- 

 paratively slight. In Tkecaphora, on 

 the contrary, the complex spore, or 

 agglomeration of spores, is compact, FlG - ^.-Thecaphora hyaiina. 

 being at first apparently enclosed in a delicate cyst. In Tubur- 

 cinia, the minute cells are compacted into a hollow sphere, 

 having lacunas communicating with the interior, and often exhi- 

 biting the remains of a pedicel. 



^ECIDIACEI. This group differs from the foregoing three 

 groups prominently in the presence of a cellular peridium, which 

 encloses the spores ; hence some raycologists have not hesitated 

 to propose their association with the 

 Gasteromycetes, although every other 

 feature in their structure seems to 

 indicate a close affinity with the 

 Cceomacei. The pretty cups in the 



genus JEttidium are sometimes scat- ^^^.3 



tered and sometimes collected in clus- FlG - 24.- 

 ters, either with spermogonia in the centre or on the opposite 

 surface. The cups are usually white, composed of regularly 

 arranged bordered cells at length bursting at the apex, with the 

 margins turned back and split into radiating teeth. The spores 

 are commonly of a bright orange or golden yellow, sometimes 

 white or brownish, and are produced in chains, or moniliform 



