62 MICROSCOPIC FUNGI. 



the same species : tlie latter we liave foimd in tlie 

 montli of May, and the former in August and 

 September. The lower leaves of young seed- 

 lings have generally rewarded us with the best 

 specimens of the septate-fruited brand {Puccinia 

 variahlUs, Grev.). The pustules occur on both 

 sides of the leaf, and are very small and scattered 

 (fig. 82). The spores are singularly variable in 

 form : sometimes both divisions are nearly equal 

 in size ; sometimes the upper,, and sometimes th& 

 lower^ division is the smallest; occasionally the 

 septum will be absent altogether; and more rarely, 

 the spores will contain three cells. From the very 

 variable character of the spores (fig. 83), th& 

 specific name has been derived. 



No species in the entire genus makes so promi- 

 nent an appearance as the one found on the radical 

 leaves of the spear thistle {Carduus lanceolatus) , 

 This latter plant is exceedingly abundant, and so 

 is- its parasite [Puccinia syngenesiarumj Lk.). From 

 the month of July till the frosts set in we may be 

 almost certain of finding specimens in any wood. 

 The leaves have a paler roundish spot, from one- 

 twelfth to one-fourth of an inch in diameter, on the 

 upper surface, and a corresponding dark brown 

 raised spot on the under surface, caused by an 

 aggregation of pustules, forming a large compound 

 pustule, often partly covered with the epidermis. 

 The individual pustules are small, but this aggre- 

 gate mode of growth gives the clusters great pro- 



