CHAPTER XII 

 TAPHRINALES 



In the Taphrinales, some hyphal cells may swell to more or less thick- 

 walled chlamydospores (gemmae) which immediately after formation or 

 after a winter's rest, germinate to an ascus. Ascospores do not arise, as 

 in the typical Ascomycetes, in the free space of the ascus, but are cut out 

 of a protoplasmic layer, adjacent to the wall. 



At present only parasitic forms of the Taphrinales are known. Accord- 

 ing to the number and method of formation of the ascospores, they 

 fall into two families, the Protomycetaceae and the Taphrinaceae. 

 In the Protomycetaceae, each of the spore mother cells, present in an 

 indefinite number along the walls, divides into four ascospores, endo- 

 spores. In the Taphrinaceae, they arise in fours or eights by free cell 

 formation, as in the typical ascus, from the protoplasmic layer at the wall. 



Protomycetaceae. — The life cycle of this family will be discussed for 

 two of the best known representatives, Protomyces pachydermus and P. 

 macrosporus; the former is found on Taraxacum officinale; the latter, in 

 various biological strains, is more or less sharply specialized on various 

 Umbellif erae ; both cause callosities on the stems and leaves of the host 

 (Popta, 1899; Biiren, 1915, 1922). 



Their hyphae are intercellular, the cells are multinucleate. They 

 swell to intercalary or terminal chlamydospores (Fig. 99, 15). From 

 youth these are multinucleate and the nuclei are often paired. Each 

 possesses a three-layered membrane, a thick, brownish, smooth exospore, 

 thin meso- and endospores (Fig. 99, 1). After a complete winter's rest, 

 they germinate. They are finely granular, somewhat turbid, with a 

 faveolate structure. The exospore ruptures and the endospore comes out, 

 in P. pachydermus as a cylindrical, in P. macrosporus as a spherical sac 

 (Fig. 99, 2). The vacuoles fuse to a large central vacuole and the proto- 

 plasm lines the wall as a homogeneous layer (Fig. 99, 3) ; probably nuclear 

 divisions take place in it. By radial fissures, the wall layer is divided into 

 uninucleate portions (spore mother cells) which, after two simultaneous 

 nuclear divisions, separate into four spores each (Fig. 99, 4 to 7). At the 

 top of the sporangium these gradually form a ball which, at the rupture 

 of the sporangium, is shot off a short distance (Fig. 99, 8 to 10). 



The spores are ellipsoidal, hyaline and uninucleate. Directly after 

 they are ejected from the sporangium, they are connected by a small 

 process and copulate (Fig. 99, 11 and 12). The nuclei enter the bridge 



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