UREDINACEAE 



289 



head white, then greenish brown. Asci cylindrical, soon 

 deliquescing, 8-spored. Spores globose, tinged brown, 4-5 ^ 

 diam. 



The fungus is most abundant in a very moist soil, especially 

 the subsoil, and drainage is an important factor in checking 



FIG. 84. Roesleria hypogea. i, fungus on root 

 of vine ; 2, ascus with spores. Highly mag. 



the pest. Diseased vines should be removed, and the soil 

 treated with lime to check the spread of the fungus in the 

 soil. 



Hartig, Diseases of Trees (Engl. ed.), p. 83 (1894). 

 Jolicoeur, Rap. sur le Malad. de la Vigne, connue dans la 

 Marne sous le nom de ' Morille'' '; Chalons-sur-Marne (1881). 

 Prillieux, Malad. des Plantes Agric.^ 2, p. 466 (1897). 

 Viala, Malad. de la Vigne^ p. 211. 



UREDINACEAE 



The uredines or rusts are undoubtedly the most pro- 

 nounced fungal parasites known. There is no single instance 

 recorded of any member of the group having passed through 

 the cycle of its development apart from its normal host- 

 plant. The various species are parasitic on all the higher 

 plants, and their distribution is only limited by that of their 

 hosts. Judging from the extreme nature of their parasitism, 

 the amount of differentiation present, and the dying out 

 in many species of phases of development which remaining 



T 



