1900 | THE HAUSTORIA OF THE ERYSIPHEZ: 171 
ERYSIPHE GRAMINIS AND OTHER SPECIES. 
The absorbing organs of Erysiphe graminis on Poa pratensis 
deserve description. It has long been known that the haustoria 
of this species are ‘branched in a peculiar manner.’”’ This fun- 
gus grows very luxuriantly on the grasses and fills the epidermal 
cells full of large branched haustoria. A shining, colorless area 
occurs around the penetrating tube (fig. 77) which is slightly 
larger than in E. communis. The colorless area is slightly 
depressed, as already mentioned. The collars of cellulose are 
relatively thick also. Fig. 19 represents nearly the maximum 
thickness for the collars in Poa. The body portion of the absorb- 
ing organ is always approximately cylindrical or ellipsoidal, with 
finger-like projections growing out from the ends or sometimes 
from only one end (figs. zg, 27). A large nucleus lies near the 
middle, and in either end, in mature examples, there is a large 
vacuole. The branches are also vacuolated. The body is not 
always symmetrical with respect to the neck (fig. 20) but the 
neck may be near one end from which, even then, branches may 
arise. The development of the haustoria of this species was not 
followed, but in none of the mature examples have the sheaths 
possessed any granular contents as found in &. communis and 
elsewhere. The sheath-membranes are usually present, though 
they exhibit great irregularities. Sometimes they are not to be 
seen except for a short distance; sometimes they completely 
Surround the haustoria, being discernible even down between 
the branches, At other times the branches penetrate the sheath. 
The protoplasmic contents of the epidermal cells are usually 
scanty. It seems impossible that the cell nucleus should escape 
destruction when the haustoria are thus provided with long 
branches. But the same indifference to the nucleus exists here 
as in Z. communis. Even when a cell contains several haustoria, 
the nucleus is usually unmolested, and is often as normal in 
appearance as in uninfested cells. This form’of absorbing organ 
may be looked upon as the result of a special effort of this spe- 
Cies to obtain abundant food. The heavy growth of mycelium 
and the immense number of conidia produced by this species 
