130 DISEASES OF CROPS. 



hos1>plant. The teleutospores (the " res ting-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 yellovsr colour. According to De Bary 

 {Monatsbericlit dev 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 

 .i&idium 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 Mcidium 

 berberidis, and that these fungi are quite distinct. If 

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

 germinate (without producing an jEcidium) on various 

 members of the Graminem, reproducing the uredo- 

 mycelium 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 

 heteroBcious 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 quau' 

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



