92 DISEASES OF CULTIVATED PLANTS 



has not been recorded in this country. May it never come ! 

 There is just the chance, however, as the author has met with 

 it in Algeria, Tunis, and in five different districts in France. 

 It was also found on a wild vine from the banks of the 

 Mississippi. 



Prunet, M. A., Comp. Rend.^ 119, pp. 572, 808, and 1233 

 (1894). 



Chlorochytrium graminis (Biisgen) attacks the root and 

 leaves of different kinds of pasture and lawn grasses ; the 

 disease spreads from a centre, killing off the herbage and 

 leaving naked patches. Species of Poa, Paniaim^ and Avena 

 are susceptible to the disease, but I failed to infect seedlings 

 of Bromus and Hordeum. If the yellow, fading, or dead basal 

 leaves are examined, the tissues, more especially along the 

 edges of the leaf, are seen to be crowded with the resting- 

 spores of the fungus. 



Resting-spores elliptic-oblong, wall smooth, almost colour- 

 less, rather thin, 35-45 X 24-32 /x. 



PYROCTONUM (PRUNET) 



Mycelium broadly effused in the matrix, consisting of very 

 delicate filaments. Zoosporangia formed from swellings of 

 the mycelium. Zoospores globose, i-ciliate, later becoming 

 clothed with a wall, about 3 /* diam. Secondary zoosporangia 

 are formed within the old primary empty ones. When badly 

 nourished the zoosporangia become changed into cysts or 

 resting-sporangia, furnished with a thick, brown wall. 



Dwarfing of wheat. A. Prunet has described a serious 

 disease of wheat caused by Pyroctonum sphaericum (Prunet) 

 one of the Chytridiaceae. The symptoms are a general arrest 

 of growth, followed by a progressive yellowing and shrivelling 

 of the leaves, but usually the entire plant is not killed for some 

 considerable time. The patches of stunted, shrivelled corn 

 in a field extend in area under favourable climatic condi- 

 tions, and may assume considerable dimensions. All parts of 

 the plant, root, stem, leaves, and flowers are eventually 

 attacked, the presence of the parasite in the ovule causing the 

 abortion of the grain. 



Mycelium branched, intracellular, broadly effused, consist- 

 ing of exceedingly slender hyphae, zoosporangia ovoid or 



