212 CLASS ASCOMYCETEAE 



are of two opposite sexual tendencies, four of each in each ascus. These 

 ascospores, or the spores that bud off from them, give rise to slender germ 

 tubes which fuse with those from spores of opposite sexual tendency, 

 producing a dicaryon mycelium which becomes the vegetative mycelium 

 within the host. Eventually some of the cells of this mycelium enlarge, 

 the nuclei fuse and the asci are formed. Thus in Botryotinia fuckeliana, if 

 Kharbush's report is correct, the mycelium and the apothecium lack 

 entirely the dicaryon phase except as the cells fuse to initiate the asci, 

 while in Taphrina the whole vegetative mycelium is of dicaryon nature. 



Some botanists suggest that the production of nonmotile sperms which 

 fuse with trichogynes and the budding out of ascogenous hyphae from 

 the oogone are indications that the Ascomyceteae may have descended 

 from some algae related to the Red Seaweeds (Florideae). Other botanists 

 (e.g., Gaumann, 1926; Atkinson, 1915; Nannfeldt, 1932) considered the 

 nonmotile cells that fuse with the trichogyne to be merely modified co- 

 nidia which have been substituted for antherids, just as certain fusions 

 of vegetative cells have taken the place of the union of sexual organs in 

 the Class Basidiomyceteae. Dangeard (1907) and the Moreaus (1926, 

 1928) deny any fusion of sperms and trichogyne, at least so far as any 

 transference of nuclei occurs. Since the author follows those that consider 

 the production of a trichogyne and nonmotile sperms and of an oogone 

 producing numerous ascogenous hyphae to be primitive characters for the 

 Ascomyceteae the orders will be arranged in a sequence according to that 

 viewpoint. This matter will be discussed in detail in Chapter 17. Those 

 botanists who take the opposite viewpoint and consider the occurrence 

 of sperms and trichogynes as representing no more than accidental con- 

 vergence of evolutionary development in both Ascomyceteae and Flo- 

 rideae would probably prefer to start with the Order Saccharomycetales. 



Order Laboulbeniales. These are minute, almost microscopic para- 

 sites upon insects. They develop externally upon the host except for a 

 haustorium or "foot" that is rooted in the chitinous body wall of the 

 host or less often may penetrate it and form a branching hyphal growth 

 in the body cavity. In the more usual form the foot usually enters the 

 body wall at a pore and thus obtains an ample supply of food without 

 penetrating clear into the body cavity. The fungi vary from plants with 

 only a few cells in number and considerably less than 0.1 mm. in height 

 to forms with hundreds of cells and 2 or 3 mm. tall. The cell walls are 

 usually thick and firm, often dark in color. Between adjacent cells which 

 have arisen by the division of a common parent cell a perforation in the 

 septum is distinctly visible as is usual in the Class Florideae. The plant 

 may consist essentially of a row of cells which give off laterally some 

 branched filamentous appendages and a female reproductive branch. On 

 or near the appendages are borne the antherids. This simple type of struc- 



