102 FUNGI. 



Uredo seg'etum is the " smut" of wheat, barley, and 

 oats a fungus too well known to the farmer. It 

 forms sooty masses, bursting through the epidermis 

 of the stalk and ears of the corn, and soiling the 

 fingers when handled. The spores (PL VII. fig. 5) 

 ar^ exceedingly minute, and the stalks are so slender 

 and loosely connected with them that they are not 

 readily detected. Under the microscope the spores 

 appear brown and faintly dotted, this appearance 

 arising from a reticulated structure of the surface, 

 similar to that of the poppy-seed on a very small 

 scale. 



Uredo caries is the " bunt " of corn. It grows 

 within the grain, filling it with a sooty, foetid mass. 

 The spores (PL VII. fig. 6) are considerably larger 

 than those of the last species, and their surface is 

 distinctly reticulated. They are attached to the fila- 

 ments of the mycelium, as in Uredo segetum. 



The spores of both these species of Uredo may be 

 found in most kinds of flour and bread, especially in 

 those of inferior quality. 



Uredo can'dida (PL VII. fig. 7) is another species, 

 forming white dots upon the leaves of the common 

 Shepherd's Purse (Capsel'la bursa pastor' is] which 

 is easily recognized by the form and arrangement of 

 the pods (fig. 19). The spores (s) are rather large 

 and white. 



Other species of Uredo are very common upon 

 numerous species of weeds or wild flowering plants ; 

 and they so closely resemble each other that, when 

 one is known, the others are easily recognized. Usually 

 each species occurs upon a distinct species of plant, 

 as is the case with parasites generally. In many of 

 them the spots (sori) exhibit a thin membrane cover- 

 ing the spores, which bursts down the middle, so as to 

 bear some resemblance to a capsule. But there is no 

 true capsule, the membrane consisting of the epider- 

 mis of the leaf or stalk of the plant, which is raised and 



