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 J 

 in Sadebeck's sense 1 , 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 stalk-cell, which rests on the substratum, and an upper cell, the club- 

 shaped asms. 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. 



