52 MICROSCOPIC FOTTGI. 



observed. There will still be a proportion of sub- 

 globose, one-celledj yellow spores ; but the majority 

 will be elongated, most with pedicels or stalks, if 

 they have been carefully removed from the leaf, and 

 either decidedly two-celled, or with an evident 

 tendency to become so. The two cells are separated 

 by a partition or dissepiment, which divides the 

 original cell transversely into an upper and lower 

 cell, with an external constriction in the plane of 

 the dissepiment (plate IV. fig. 59) . These bUocular 

 or two-celled spores are those of the " corn mildew " 

 (Puccinia graminis), which may be produced iri the 

 same pustules, and from the same myceHum, as the 

 " corn rust," but which some mycologists consider 

 to be a distinct fungus, others only a modification or 

 stage of the same fungus. After an examination of 

 the difierent forms in the aUied genera to which 

 these chapters are devoted, we shall be able with 

 less of explanation and circumlocution to canvass 

 these two conflictirig opinions. 



Let us proceed, for the third and last time, to 

 our cornfield, when the corn is nearly or fully ripe, 

 or let us look over any bundle of straw^ and we 

 shall find blackish spots, from the size of a pin's 

 head to an inch in length, mostly on the sheaths of 

 the leaves, often on the culm itself. This is the 

 fully developed mildew, and when once seen is not 

 likely afterwards to be confounded with any other 

 parasite on straw (fig. 57). The drawings of Bauer 

 have already been alluded to. Bauer was botanical 



