An Examination of the Species of the genus 
Doassansia, Cornu, 
BY 
WILLIAM ALBERT SETCHELL 1 . 
With Plates I and II. 
U P to the present time there have been twelve species of 
Doassansia described. The genus was founded by 
Cornu in 1883 (Ann. Sci. Nat., ser. 6, T. 1 5, p. 285), to receive 
the Perisporium alismatis of the Systema Mycologica of Fries 
(vol. iii, p. 252). Cornu found abundance of this species in the 
neighbourhood of Paris, and was able, by a careful study of 
its development, to establish it firmly among the Ustilagineae 
in close proximity to the genus Entyloma. He says, that the 
spores of this form on Alisma resemble closely those of Enty- 
loma both in their structure and in their method of germi- 
nating, but are collected and compacted into bundles or ‘ sori,’ 
which are enclosed by a coat or ‘cortex’ of sterile cells. It 
is this cortex of the sorus which Cornu considers to be cha- 
racteristic of the genus, and he has been followed by later 
writers in so considering it. D. alismatis , which must be looked 
upon as the typical species, possesses a very distinct and well- 
developed cortex. 
In the same paper Cornu describes a second species, sent by 
Farlow from North America, which causes marked distortions 
of the ovaries of species of Potamogeton. He states that this 
1 Contributions from the Cryptogamic Laboratory of Harvard University, 
No. XVIII. Prepared under the direction of Prof. W. G. Farlow. 
[Annals of Botany, Vol. VI. No. XXI. April, 1892.] 
B 
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