' MILDEW ' OF WHEAT 731 



end of which a single small transparent conidium or basidio 

 spore (b) is abstricted. 



It is still an open question whether these basidiospores nan 

 infect wheat plants ; it is usually assumed that they cannot do 

 so, and with one exception experiments to test the matter have 

 yielded negative results. However, when placed upon the leaf 

 of a barberry bush {Berberis vulgaris L.) they germinate and 

 produce a delicate hyphal filament, which penetrates into the 

 leaf and develops a mycelium there. Upon this mycelium 

 are produced extremely minute oval conidia (formerly termed 

 spermatid) and chlamydospores, which are known as cecidiospores. 



The conidia arises in chains on the ends of delicate hyphse 

 within a pear-shaped structure, the so-called spermogonium, which 

 is formed of closely interwoven hyphse, usually situated beneath 

 the upper epidermis of the barberry leaf (compare B, Fig. 248). 

 Although they can be made to germinate in solutions of sugar or 

 honey, the small conidia appear to be functionless under natural 

 conditions and the part which they play in the life-history of the 

 fungus is unknown. 



The secidiospores are produced in yellow cup-like structures 

 or cecidia, which grow in clusters upon swollen patches on the 

 lower surface of the barberry leaf (compare A, Y\g. 248). When 

 mature each secidium resembles a cup with an irregularly torn 

 margin which is bent outwards. At the base within the cup 

 are numerous short hyphas very closely packed together ; above 

 these and filling the cup are the ascidiospores arranged in the 

 form of long chains {B, Fig. 248), each spore being at first separated 

 from the next by a short temporary intermediate cell. The 

 secidiospores ultimately become free from each other and are 

 distributed by the wind and rain. They are roundish single 

 cells with orange-yellow contents, and a colourless, almost 

 smooth epispore in which are several germ-pores. Their vitality 

 lasts but a few days. When placed on a barberry leaf and 

 allowed to germinate, they do not penetrate the leaf or re- 



