of the Genus Doassansia , Cornu . 45 
Genus III. Cornuella, gen. n. Sorus consisting of a firm 
layer of spores on the outside, and of loose hyphae on the 
inside. Cortex absent. 
C. lemnae , sp. n. Spot none. Sori globular to ellipsoidal, 
50-70 [i in diameter, brownish black. Hyphae of the central 
part of the sorus brown. Spores borne at the tips of hyphae, 
inseparable at maturity, 10-12 ix by 6-10 fx. Promycelium 
obconical, about 16 /x long. Sporidia in whorls of from 5 to 7, 
about 2 6 ix long by 2 /x broad. 
On Lemna ( Spirodela ) polyrrhiza. 
Belchertown, Mass., Prof. J. E. Humphrey ! Newton and 
Cambridge, Mass. ! 
Relationships. 
About the genus Title tia are clustered a number of distinct 
genera, closely related to it both in type of spore and in 
type of germination, but differing widely from it in the 
complexity of the structure of their compound sporophores. 
Such are the genera Urocystis and Tuburcinia , and perhaps 
also Sorosporium , Cintractia , and Testicularia. When De 
Bary in 1874 (Bot. Zeit. p. 81) established the genus 
Entyloma , he recognised its near relationship to Tilletia as 
well as its distinctness from it. Since then, numerous 
additions have been made to the genus, until at present it 
contains about 40 species of very diverse structure and habit. 
Some of these, as e. g. E. crastophilum , Sacc., are of much 
more complex structure than the simpler typical species, 
such as E. microsporum (Ung.), Schroeter, E. lobeliae , Farlow, 
&c. When, in 1883, Cornu proposed the genus Doassansia , , 
it seemed probable that there might be a series of generic 
types clustered about Entyloma as well as about Tilletia. The 
present paper has endeavoured to describe a number of these 
types, several of which bear a striking likeness to generic types 
of the Tilletia-'g roup. 
The spores of the simple species of Entyloma are more or 
less scattered through the substance of the part of the leaf 
