of the Genus Doassansia , Cornu . 29 
upper surface of the spot, which call to mind the appearance 
of the conidia in certain species of Entyloma. 
The sori are situated just above the lower epidermis in the 
large air-cavities which abound in the spongy parenchyma. 
They are nearly globular, and are from 100/x to i6ojut in 
diameter. In structure they are almost identical with D. occulta 
(type), as described above. The centre is composed of paren- 
chymatous cells ; around this is a single layer of spores, which 
are slightly elongated radially, and which measure 12 \i by 6 {i 
to 8 /x ; a cortex of brown cells outside the spores ; and around 
the whole a covering of scanty hyphae. 
The development of the sorus agrees perfectly with that of 
D. occulta . At first the ball of hyphae shows a concentric 
arrangement ; soon there appears at the centre a small darker 
portion, which, as it increases in size, takes on a radiating 
structure, and appears more of a yellowish brown than the 
coat of concentric hyphae, which gradually grows thinner 
(Fig. 80). The steps by which the spores, cortex, and central 
cells appear could not be detected in the dried material. 
The mycelium is abundant in the intercellular spaces of the 
infected portion of the leaf, and forms tangled masses in the 
dome-shaped cavities under the stomata of the upper surface. 
Bunches of short unbranched hyphae extend up through the 
stomata, and end somewhat bluntly. But at the tips of some, 
long slender spores were attached, much resembling the conidial 
spores of Entyloma. These spores are about 30 \ u long and 
i\5 ju wide. They apparently germinate in position, and thus 
give rise to small bunches of tangled hyphae. There can be 
little doubt that they belong to the Doassansia , but further 
study from the living material is highly desirable. 
Schroeter (Pilzfl. Schles. p. 287) seems inclined to consider 
that these two species, the one inhabiting the ovaries and the 
other the leaves of species of Potamogeton , are identical. There 
is little difference between the sori of the two species : the 
chief differences are in habit. D. occulta causes a considerable 
distortion in the species which it inhabits ; D. Martianoffiana 
none at all. But the fact that D. occulta causes a distortion 
