CHAPTER V.—COMPARATIVE REVIEW.—DOUBTFUL ASCOMYCETES. 265 
on the tips of the branches of the young appendage, and these also subsequently dis- 
appear. According to Karsten these small swellings, which are spherical in Stigmato- 
myces, separate in that plant from the cells on which they are formed and attach 
themselves to the protuberance on the young perithecium, as spermatia in the Fungi 
or Florideae attach themselves to the trichogyne, and then the spores or asci are 
developed from an axile cell. If this were so, the organs in question would have to be 
termed sexual organs and their homologies with the sexual organs of the Ascomy- 
cetes would be evident enough. But it appears from Peyritsch’s careful observations 
that no such supposed abscision of spermatia really takes place. We know nothing 
more than has been stated above, and Peyritsch himself does not think very highly 
of his own attempt to save the trichogyne, which might be fertilised by contact with 
a young branch from the appendage. It is not yet quite certainly ascertained 
whether the asci are formed by division or by sprouting from one or more initial cells. 
With these data only to guide us, it will be best for the present to allow the 
remarkable little group to remain next the Ascomycetes, being marked as doubtful, 
till further information is obtained concerning them. 
Section LXXVI. The species of Taphrina, Fr., the Exoascus of Fuckel 
in Sadebeck’s sense‘, are parasites developing on the surface of parts of living 
plants, which are more or less deformed by them; Exoascus Pruni, for example, 
grows on the young fruit of species of Prunus, and produces swellings in them which 
are known as pockets, more rarely on the leafy shoots, while E. aureus is found on 
the leaves and ovaries of Poplars and Aspens and E. alnitorquus on the deformed 
fruits and upon leaves of the Alder. 
The Fungus when fully developed is composed chiefly of a single palisade-like 
layer of asci standing close beside one another, which breaks through the cuticle and 
covers the outer surface of the epidermis of the part attacked. The species which 
live on the Amygdaleae, Exoascus Pruni for example and E. deformans, develope 
this layer from a filiform mycelium, which first spreads in the inner parenchyma of 
the part and then thrusts its branches in between the outer walls of the epidermal 
cells and the cuticle. In this situation the branches ramify copiously, and spread 
out in the direction of the surface, the ramifications, which grow alongside and 
between one another, forming a single layer and then becoming divided into 
isodiametric cells. Each of these cells next swells into a vesicle, and breaking 
through the cuticle elongates in a direction perpendicular to the substratum and 
becomes club-shaped, and at length divides by a transverse wall into a lower cell, 
the short szalk-cell, which rests on the substratum, and an upper cell, the club- 
shaped ascus. The connection of the ascus-layer thus formed with the intra- 
matrical mycelium can be seen even when the asci are mature. 
Other species, Exoascus alnitorquus for instance and E. aureus, according to 
Sadebeck’s and to some extent also of Magnus’ earlier investigations, spread their 
mycelium only between the cuticle and the epidermis. Then, as the plant developes, 
all the hyphae become divided into ascogenous cells, and these proceed as in E. Pruni; 
consequently asci only are to be seen when the fructification is mature, and these 
are either borne on a stalk-cell (E. alnitorquus) as in E. Pruni, or have no stalk 

1 In Winter, Pilze, II. 
