256 STKUCTURAL BOTANY 



simpler to speak of the whole body as a bicellular spore. 

 Within the protoplasm of each cell are two nuclei, which 

 appear subsequently to fuse into one, and there is also 

 a vacuole containing oil. The surface of the cell-wall is 

 smooth, unlike that of the uredospores. Each cell has 

 a germ-pore, that is to say a deep pit in its membrane ; 

 in the upper cell this pit is situated at the apex, while 

 in the lower it lies on one side, just below the septum 

 (Fig. 102). These teleutospores represent the resting- 

 stage of the Fungus, in which it passes through the 

 winter. 



This completes the history of the parasite, so far as its 

 life on the Wheat or other gramineous * host is concerned. 

 The damage which it does to the crop is very serious, 

 though its immediate effect is only local. The chloro- 

 phyll of the part attacked is destroyed, and the tissues 

 thus rendered useless for assimilation, while the cells 

 affected ultimately become exhausted and die. Thus, if 

 the seats of infection be numerous, the plant may 

 gradually lose almost the whole of its effective leaf- 

 surface, and thus become starved and quite incapable 

 of producing good grain. 



The germination of the teleutospores in this species 

 takes place in the following spring. Each cell sends out 

 a hypha, which starts from the germ-pore, as shown in 

 Fig. 102. These hyphse never develop into a normal 

 mycelium, but are of strictly limited growth, forming 

 what is called a pro-mycelium (see Fig. 102), which 

 divides by transverse walls, cutting off a row of about 

 four cells from its terminal portion. Each of these cells 

 sends out a slender lateral outgrowth, which swells up 

 at the end to form a small spore-like cell (Fig. 102). 



1 The natural order Gramiueae, or Grasses, includes all cereals, 



