1882.] 



Development of Peritheciwn of Meliola. 



389 



much, branched mycelium consists of jointed cylindrical hyphae, with 

 hardened brown or black cell-walls and finely granular protoplasmic 

 contents ; these are closely attached to the epidermis of tropical 

 plants by rudimentary haustoria, which are closely adherent to the 

 cuticle, but do not pierce the cells of the host. 



The mycelium supports setaceous appendages of various forms, 

 simple or branched ; these setai spring from scattered points along the 

 course of the hyphae, and are especially developed from around the 

 fruit-bodies, arising from richly branched hyphae in their neighbour- 

 hood. Bornet considered these as forming a special part of the fungus, 

 under the name of the " receptacle," but development teaches that 

 they cannot be regarded as of importance ; no special function can be 

 assigned to the setce, and they are certainly not tubes for the outlet of 

 the spores, as earlier observers surmised. 



Other appendages occur as short, lateral, pyriform, or flasked-shaped 

 branchlets ; some of which become free, and develope new mycelia by 

 budding, much as is the case with the conidia of Erysiphe and allied 

 fungi. Others give rise to the Perithecia , which are globular or sub- 

 globular cases containing asci in their interior, and with hard black 

 outer cell- walls. 



The author has studied the origin and development of the Peri- 

 thecium very particularly. A short ovoid or pyriform lateral branch- 

 let becomes cut off as a unicellular body, by a firm septum close to 

 the parent hypha ; this cell is next divided into tw o by a cell- wall 

 passing obliquely across it. Of the two cells thus produced, one divides 

 more slowly, and forms a mass or "core" of thin-walled cells, with 

 richly developed protoplasmic contents ; the other, dividing much 

 more rapidly, produces a layer of cells, which gradually envelopes the 

 " core " of thin- walled cells, and forms the outer walls of the Peri- 

 thecium. 



The " core " of more slowly dividing thin- walled cells is an asco- 

 gonium ; in later stages, certain of its constituents are seen to form the 

 ■asci and spores, while others deliquesce and serve as nutritive material. 

 The outer walls of the enveloping layers become thick, hard, and 

 dark-coloured; the inner cells of the series deliquesce, and serve for 

 nutrition of the young asci, &c, as before. All these processes are 

 recognised in vertical sections of the young Perithecium in various 

 stages, and are figured and described in detail. 



The asci are delicate clavate sacs, developed successively, and con- 

 taining two to eight uni-tri-septate spores, the formation of which is 

 also figured. The germination of the spores was also examined ; each, 

 puts forth a germinal tube, which soon developes a rudimentary haus- 

 torium, and becomes irregularly branched, finally growing forth as a 

 mycelium like that first described. 



The author examines and criticises the views held by Fries and 



