PUCCINIA 305 



it would have been more convincing if Ward had obtained 

 from Eriksson some of the barley which the latter stated to 

 become rusted when grown in sterilised soil, and under 

 conditions that excluded the chance of external infection. 



Whether Eriksson's mycoplasm theory proves to be correct 

 or not, I am inclined to believe his idea that spores alone do 

 not account for the enormous and simultaneous appearance 

 of rust over extensive areas under certain weather conditions, 

 and consider that as in the case of rye-grass fungus, potato 

 disease, Sclerospora in cereals, etc., the explanation will be 

 found in the form of hibernating mycelium. Dr. Butler, 

 Imperial Mycologist, Simla, India, judging from the follow- 

 ing extract, entertains a somewhat similar view : 



'No entirely satisfactory explanation has yet been given 

 of the way in which the disease originates each year. There 

 is strong reason to believe that it cannot arise from spores 

 from the previous crop, nor to any great extent from other 

 grasses affected with the same rusts. No "intermediate" 

 host (bearing the fungus in the aecidial stage) has been 

 found, nor is likely to be found which can commonly pro- 

 duce the disease in the greater part of the infected area. A 

 hereditary origin is possible through the use of infected 

 seed, but is not proved so far as India is concerned.' 



Aecidium stage. Aecidia shortly cylindrical, edge spread- 

 ing and torn ; spores subglobose, smooth, yellow, 14X16/* 

 diam. Spermogonia on opposite side of leaf to aecidia. 



Uredo stage. Sori forming rust-coloured streaks 2-3 mm. 

 long, sometimes much longer; spores broadly elliptic, dingy 

 yellow, spinulose, 17-40X 14-22 [x. 



Teleutospore stage. Sori forming blackish streaks up to 

 10 mm. long; spores fusiform or club-shaped, with a long 

 pedicel, smooth, chestnut-brown, apex rounded or narrowed, 

 wall thickened, 35-60 X 12-22 \i. 



No preventive measures are known, and the production 

 of immune varieties of w T heat appears to afford the only 

 hope of preventing loss. Professor Biffen, of Cambridge, 

 has already made substantial progress in this direction. 



Butler, Mem. Dep. Agr. India, Bot. Ser. 1, No. 2. 

 Eriksson, Bot. Gaz., 25, p. 26 (1898). 

 Eriksson and Henning, Die Getreideroste, 1896. 

 Ward, Ann. Bot., 11, No. 6 (1888). 



Crown rust of cereals. A widely distributed rust, caused 



U 



