50 ASCOMYCETES [ch. 



comparison of the sporogenous filaments of a Red Alga with the ascogenous 

 hyphae, of the algal trichogyne with the unicellular trichogynes of some 

 Ascomycetes, and of the spermatia in the two groups is certainly suggestive, 

 but it assumes that the trichogyne in the two cases is homologous, a very 

 doubtful point, and it involves the corollary that all the simpler Ascomycetes 

 are derived by reduction from the more complex. 



The derivation of the group from the Phycomycetes was upheld by 

 Winter in 1874, by de Bary in and after 1 881, by Brefeld in 1889, and lately 

 by Atkinson 1 in 19 14. 



Any conclusion however, as to either the origin or the inter-relationships 

 of the Ascomycetes, must await a detailed knowledge of the development 

 of the ascocarp and of the morphology of the sexual apparatus in a much 

 larger number of species. 



So far the development of the ascocarp throws little light on the problems 

 of phylogeny; in the great majority of cases the ascogenous hyphae are 

 enclosed when young by a weft of gametophytic filaments, and, in the 

 simplest of such cases, this arrangement persists till the asci are ripe and 

 the gametophytic hyphae decay. In other cases there is a considerable 

 variation in the time and extent of the opening of the fructification, though 

 its mature form is of two main types. In view of this fact it is clear 

 that the Pyrenomycetes, in which the perithecium is flask-shaped, opening 

 by an ostiole, and the Discomycetes, in which the apothecium is typically 

 cup-shaped and wide open at maturity, are justified as form groups and this 

 long established arrangement is not contradicted by what we know of the 

 development of the sexual organs. 



The Discomycetes show three types of sexual apparatus: 



(1) The oval antheridium and somewhat elongated, coiled archicarp of 

 Ascodesmis. Here the archicarp ends in a one-celled trichogyne and the 

 unicellular oogonium becomes septate after fertilization and gives rise to a 

 few short ascogenous hyphae-. 



(2) An oval antheridium, unicellular trichogyne,and more or less spherical 

 oogonium which does not undergo septation. This type is found in Pyronema, 

 and may be traced in Humaria granulata, and presumably in other forms 

 where a large oval cell has been seen at the base of the developing ascocarp. 

 It is present also in Lachnea stercorea, if the septate trichogyne of this species 

 can be looked upon as a secondary development. It is the characteristic 

 type of the Pezizaceae. 



(3) A scolecite or stout septate archicarp, the distal cells of which form a 

 trichogyne and the proximal a stalk, while the middle region is multicellular, 



1 Ann. Mis. Bot. Card. 1914, ii, p. 315. 



- Another simple form is Thelebolus. which shows certain suggestive analogies to Sphaeiotheca, 

 but demands further investigation. 



