84 MICROSCOPIC FUNGI. 



salveiiy and externally bears considerable resem- 

 blance_, except in tlie size and colour of the spores 

 (fig. 119)^ to another species much, more common^ 

 and which occurs on the leaves of Poa aqitatica and 

 P. fliiitans. 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 Y. 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 Aira ccespitosa 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 U. longissima. 



Sedges are also subject to attack from other 

 species of smut; one of these (Z7. olivacea) appears 

 to convert the seeds into a fine olive-coloured dust 

 (plate VI. 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 

 naore than in any other species^ and_, though larger 

 than the normal seeds^ still retaining their form 

 (figs. 109^ 110). This is Ustilago iirceolorumj the 

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



The beaksedge {Wiyncospora alba) suffers from 



