130 DISEASES OF CBOPS. 



host-plant. The teleutospores (the " resting-spores " of 

 Plowright) hibernate until the following spring. They 

 then germinate (Fig. 45 C), and subsequently give rise to 

 a short pro-mycelium bearing transparent oval-shaped 

 spores of a yellow colour. According to De Bary 

 {Monatsbericht der Koniglichen Preuss. Akademie der 

 Wissenschaften zu Berlin, 1865), Plowright {British 

 Uredinece and Ustilaginece), Carruthers, Sachs, and other 

 botanists, the pro-mycelium spores of this fungus germi- 

 nate on the leaves of Berberis vulgaris (the common 

 barberry bush) giving rise to the fungus known as 

 .^Ecidium berberidis, whose spores are said to reproduce 

 the uredo-mycelium, or the first stage in the life-history 

 of Puccinia graminis. On the other hand, Cooke, 

 Berkeley, Smith, and others state that there is no genetic 

 connection between Puccinia graminis and .^Icidium 

 berberidis, and that these fungi are quite distinct. If 

 the latter idea is correct, the pro-mycelium spores must 

 germinate (without producing an .^kidium) on various 

 members of the Graminece, reproducing the uredo- 

 myceKum and its spores. 



According to De Bary's school of fungologists, the 

 " summer corn mildew " completes its life-history by 

 alternately living upon two separate plants ; it is, there- 

 fore, a dimorphic, hetercecious, or metoecious fungus. Mr. 

 Plowright (see his book, loc. cit.) states that forty-seven 

 hetercecious species of the Uredinece are now known, and 

 the life-history of eleven of these was first worked out by 

 himself. 



It is well known that parasitic mildews cause putre- 

 factive changes to occur within the tissues, etc., of infested 

 plants. The author detected the presence of small quan- 

 tities of alcohol and lactic acid in the sap of infested or 



