:8 British UredinecB and UstilaginecB, 



CHAPTER V. 



UREDOSPORES. 



The uredospores may be developed from mycelia pro- 

 duced from the entrance of the germ-tube of an aecidio- 

 spore, a promycelial spore, or another uredospore. The. 

 uredospores are developed singly on the ends of separate 

 mycelial hyphae (sterigmata, basidia). Their development 

 is as follows : — the mycelial hyphas in the affected host- 

 plant at certain points become interwoven and intertwined, 

 and the hyphae which constitute these favoured points are 

 more richly branched and more freely septate than is the 

 case in other parts of the host-plant. In them may be 

 observed a number of orange granules. The hyphae are 

 so crowded together in the spore-bed, that to a great 

 extent they lose their individual outline. Spore-formation 

 takes place, first towards the centre of the bed, and then 

 extends centrifugally. The mycelial aggregations take 

 place just beneath the cuticle of the plant, to which their 

 upper surfaces are parallel ; they are termed spore-beds, or 

 sori (sporenlager, stroma, hymenia, clinodes). Each spore- 

 bed consists of an accumulation of hyphae, which ramify 

 in all directions ; but those hyphae that are nearest to the 

 cuticle of the host-plant give off a number of branches 

 parallel to each other, at right angles to the spore-bed 

 below, and the host-plant cuticle above. Each of these 



