DOASSANSIA. 323 



through the wall, remains thin, but on emerging into an inter- 

 cellular space it soon thickens and branches into a mycelium. 

 Infection results in the appearance of yellow spots, due to 

 rapid destruction of the chlorophyll and death of cell-contents. 

 Experiments in germination have been carried out by Setchell 

 and Brefeld.^ 



Doassansia sagittariae (West.) (Britain and U.S. America). 

 In leaves of Sagittaria. The spores, according to Brefeld, 

 germinate in water, after hibernation. They produce unicellular 

 promycelia with a terminal tuft of more or less spindle-shaped 

 conidia, which at once begin to sprout and fall off. On the 

 surface of a nutritive solution they continue to sprout yeast- 

 like, and form close mouldy coatings. {Doassansia is the only 

 genus of the Tilletiae in which Brefeld found yeast-like sprout- 

 ing of conidia.) 



D. alismatis (Nees) (Britain and U.S. America). This 

 inhabits leaves of Alisma Plantago and A. natans, producing 

 knotty swellings. The spores are enclosed in a layer of com- 

 panion-cells containing air, whereby the masses swim on water. 

 On the promycelium the conidia arise from tufts of conidio- 

 phores ; they fuse in pairs, and secondary conidia are developed 

 from each pair or even from single conidia. 



D. Niesslii (de Toni) forms small spots on leaves of Buto- 

 mus umbellatus. The spores are surrounded by companion-cells 

 containing air. They germinate before leaving the spore-patch, 

 and produce conidia, even secondary conidia, before rupture of 

 the host-epidermis takes place. Brefeld describes the spores 

 as germinating in water to form a very short promycelium 

 with short thick conidia which fuse in pairs and give off larger 

 secondary conidia from their apices. In nutritive solution 

 conidia are developed, which give off septate filaments whence 

 further conidia arise. Aerial conidia are ultimately developed. 



Magnus found that the spores of I), alismatis, D. Niesslii, 

 and other species germinated at once on reaching maturity. 

 Brefeld, however, found that this took place only after they 

 had lain over winter. It may be that here, as with some 

 higher plants {e.g. Pimis Ceimhra), there is an immediate 

 capability of germination, but also a deferred, the latter requiring 



1 Setchell, Annals of Botany, vi., 1892. Brefeld, SchimmelpUze, Heft xii., 

 1895. 



