19 
of the Genus Doassansia , Cor mi. 
Protomyces comari, Berl. et De Toni, in Sacc., Syll. Fung., Vol. VII, 
p. 321. Mar. 1888. 
Doassansia comari , De Toni et Massee, Journ. Myc., Vol. IV, p. 18. 
Mar. 1888. 
De Toni, in Sacc., Syll. Fung., Vol. VII, p. 506. Oct. 
. 1888. 
Doassansia obscura, sp. n. 
While searching for D. opaca , I found growing upon 
the petioles and peduncles of the same host ( Sagittaria 
variabilis , var. latifolia) an inconspicuous form which is 
clearly different from any other form either described or 
distributed. It lives in the petioles and peduncles, generally 
somewhere in the lowest third. Occasionally some sori are 
found situated half or two-thirds of the way up, but it is 
at the very base, in the parts protected by the bases of the 
dead or living leaves and destitute of chlorophyll, that it is 
most abundant. It is most frequently found also in the 
petioles of the outer and older leaves of the plant. When 
found in the petioles of the inner leaves of the plant or in the 
peduncles, it occupies, as a usual thing, a higher position than 
it does when found in the outer petioles. 
When it occurs in parts possessing chlorophyll, it produces 
a very pale yellow indefinite spot, which is scarcely noticeable 
except when closely examined. But in the bases of the 
petioles, where there is no chlorophyll, its presence may be 
detected by the dark lines where the brown sori show through 
the more or less transparent outer tissue. It produces no 
distortion at all, and is therefore likely to escape the notice 
of the collector. The easiest way to detect it is to pull off 
the outer leaves of the Sagittaria and examine the bases of 
their petioles. 
The inner portion of the petiole of Sagittaria variabilis 
contains large intercellular spaces shaped like the interior of 
a closed cylinder, with the long axis parallel to the long axis 
of the petiole. The Doassansia prefers the outer cylinders ; 
the mycelium forms a cobweb-like network in each space 
C 2 
