84 MicRosconc fungi. 



salveii, and externally bears considerable resem- 

 blance, except in tlie size and colour of tbe spores 

 (fig. 119), to another species mucli more common, 

 and wliicli occurs on the leaves of Poa aquatica and 

 P. jiuitans. The last-named species forms long 

 parallel sori, extending often for several inches along 

 the leaves of the aquatic grasses just named, giving 

 them a very singular appearance (plate V. figs. 105, 

 106). The spores are small (fig. 107), not being more 

 than one-fourth the length of the last species, and 

 smooth, whilst those are minutely granulated. 



An interesting species occurs, very rarely, on 

 the stems of such grasses as Air a ccesjntosa and 

 A. aquatica. The sori are in bands at regular dis- 

 tances apart (plate VI. fig. 120), each band being 

 composed of a number of short parallel sori (fig. 

 121). The spores are not more than one -third of 

 the size of those in Z7. longissima. 



Sedges are also subject to attack from other 

 species of smut; one of these [JJ. oUvacea) appears 

 io convert the seeds into a fine olive-coloured dust 

 (plate YI. fig. 126), which gives to the fruit a similar 

 appearance to that presented by corn when attacked 

 by Ustilago segetum. Another species, which also ab- 

 sorbs the seeds, becomes hardened and consolidated 

 more than in any other species, and, though larger 

 than the normal seeds, still retaining their form 

 (figs. 109, 110). This is Ustilago urceolorum, the 

 spores of which are also figured (fig. 111). 



The beaksedge {RlyncosiJora alba) sufi'ers from 



