1900] THE HAUSTORIA OF THE ERYSIPHEA: 155 
reach maturity, but withered and died. He concluded that the 
fungus was a true parasite on the vines and produced the disease. 
In 1853 Von Mohl (34) attempted a serious study of the weather 
conditions under which the fungus was able to accomplish such 
destruction. He examined the infested leaves more carefully 
and learned that the brown spots on the leaves appeared wher- 
ever the fungus was attached. At the brown spots the hyphe 
produced irregular outgrowths for attachment, which he called 
Haftorgane. He strongly objected to the belief of Amici (1) of 
the Italian commission, who reported that the appearance of 
mildew on the vine was a proof of disease in the plant rather 
than the cause of the disease. This was the opinion also of 
Léveillé (19). Von Mohl cited in support of his proposition 
that the mildew produced the disease, the opinions of Visiani 
and Zanardini, of the Venetian commission. Zanardini (38) had 
observed in 1851 the protrusions by which the fungus appeared 
to attach itself, and called them fuera. Von Mohl credits 
Zanardini, therefore, with the discovery of these Haftorgane. 
According to Von Mohl (34, p. 594) Visiani believed that he had 
found root-like organs arising from these Haftorgane and pene- 
trating into the epidermal cells of the grape leaves. But Von 
Mohl did not accept Visiani’s observations as correct, for he had 
seen only the surface organs of attachment and supposed they 
acted as suckers for imbibing nutriment. It seems probable, 
then, that Visiani was the first to see what we now call haustoria, 
and in his comparison of them to the roots of higher plants, he 
was the first to obtain a conception of those functions by which 
the parasite nourishes itself. Thus, as the structure of the fungus 
became better known, the general notion of parasitism took 
more definite shape. 
Berkeley (6) believed with Von Mohl that the fungus caused 
the disease, and that the surface organs of attachment, which 
Frank (14, p. 556) has so well named appressoria, were 
Suckers which drew up the juices of the host plant. Indeed, 
Berkeley (5) and subsequently other English writers applied the 
term fulcra to the appendages of the perithecia, and Berkeley at 
