248 ROMANCE OF LOW LIFE AMONGST PLANTS. 



over the leaves, as if dusted with snuff. This powder 

 consists of ovate, or almost globose, pale brown 

 uredospores, with a finely warted or delicately spinu- 

 lose coat. The mass of spores contained in each 

 pustule originates from a sort of cushion, or spore- 

 bed, composed of interwoven threads of mycelium. 

 As they grow and enlarge, the cuticle of the leaf is 

 ruptured, and the uredospores escape. This condition 

 goes by the general name of " rust," and is the second 

 stage. When fully matured these spores are capable 

 of immediate germination, each spore having two or 

 more perforations in the outer wall, through which 

 the germinating tube is protruded. The spore-bed of 

 each pustule continues to produce a succession of 

 uredospores for a considerable time. The germinat- 

 ing tube of each spore is capable of penetrating into 

 the host plant through the stomata, and producing 

 there a new mycelium, eventuating in a new spore- 

 bed, and a fresh pustule. 



From June to August the same leaves, for the most 

 part, produce smaller and darker pustules, which 

 otherwise resemble those of the uredospores, but the 

 results are different, since the powder, which is dark 

 brown, consists of spores of another type, more 

 elongated, and divided in the centre by a transverse 

 partition into two cells, seated on a colourless stem. 

 This kind of spore is termed a teleiitospore, and, when 

 each of the three stages was supposed to be a com- 

 plete and perfect fungus, these bicellular spores were 

 called Pnccmia, a name now applied to a combina- 

 tion of all three stages. Each cell is perforated by a 

 pore, through which, in germination, the germ-tube is 



