156 BOTANICAL GAZETTE [MARCH 
least believed that they thereby absorbed nutriment from the 
leaves (2). Later, however, he wrote, ‘It is very doubtful 
whether they extract anything from the matrix” (7). 
De Bary (12) seems to have been the first to work out the 
structure of the haustoria. His contributions to the subject are 
by far the most important and embrace the most of what is 
known of these organs. He applied the name haustoria, how- 
ever, both to the exterior organs of attachment (Von Mohl’s 
Haftorgane) and to the absorbing organs of the fungus, which he 
found within the epidermal cells of the host leaves. Frank (14, 
p. 556), at a later date, named the Haftorgane appressoria, reserv- 
ing the term haustoria for the real organs of absorption. Of 
haustoria De Bary distinguished three sorts (12, p. 26): (2) 
haustoria exappendiculata, found in Sphzrotheca, Podosphera, and 
such forms of Erysiphe as have two-spored asci, the. haustoria 
originating directly from mycelial filaments, which show little or 
no contortion at the points where the haustoria arise ; (2) hausto- 
ria appendiculata, the haustorium arising from a somewhat hem- 
ispherical protrusion of the hypha, z. ¢., from an appressorium ; 
(c) haustoria lobulata, or \obed appressoria. In his Comparative 
Morphology (11) De Bary defined haustoria as “special organs 
of attachment and suction,” arising in the Erysiphee, from sep- 
tate mycelial hyphae. At this point the hypha is firmly attached 
to the epidermis of the host and sends the very minute hausto- 
rial branch directly through the outer wall of the host cell. 
Within the cell the branch enlarges into “an ellipsoidal or 
somewhat elongated vesicle filled with protoplasm, which in 
Erysiphe graminis is branched in a peculiar manner.” The 
description in his Beitrage (12) is more detailed. Up to the 
point where the haustorial branch within the cell enlarges to 
form the body of the absorbing organ, the slender branch is 
apparently thick walled. This is not actually the case, for be 
to that point it is surrounded by a tube-like offset from the epi- 
dermal wall which the haustorium pierces. In cross secton, the 
neck of the haustorium would, therefore, be represented by + 
small circle, surrounded by a broad shining ring from the 
