238 DIVISION II. COURSE OF DEVELOPMENT OF FUNGI. 



which have been made in previous sections. I shall return in a later page to the matters 

 which, as I have said, do not belong to this place. 



DETERMINATION OF IMPERFECTLY KNOWN ASCOMYCETES. 



SECTION LXVII. The facts detailed in the foregoing pages were established at 

 first from a comparatively small number of species, but they nevertheless enable us to 

 pass judgment with tolerable certainty on all the varied phenomena which have been 

 observed in the countless forms of the Ascomycetes, especially the Pyrenomycetes 

 and the Discomycetes ; they are a frame in which the latter may be set. It must at 

 the same time be remembered that very many of these phenomena were known, 

 named, and provisionally disposed of according to the best knowledge of the time 

 before a secure basis was laid for a decision respecting them, and that it 

 was by starting from single phenomena that this basis was gradually reached. 

 Especially should it be remembered (see section XXXII) that at first every distinct 

 form was supposed to represent a distinct species ; the gonidiophores of Sclerotinia 

 Fuckeliana were made a species under the name of Botrytis cinerea, the sclerotia 

 another species as Sclerotium echinatum, while the sporocarps by themselves were 

 made a species of Peziza; in Erysiphe the gonidiophores were supposed to be a 

 species of the genus Oidium, and only the perithecia were assigned to Erysiphe. 

 The researches of Tulasne first led gradually to an understanding of the real 

 condition of things to which' he gave the name of pleomorphism, and to him we are 

 chiefly indebted for the distinguishing and naming of the possible forms in the 

 development of a species. These researches rested on the broad foundation of the 

 comparative observation of numerous forms, of their cohabitation, of their anatomical 

 connection, and their succession in time. Pursued in this way they arrived on the 

 whole at the truth, and it is a small diminution of their merits that they should have 

 given rise to some erroneous views on special points, or that they occasionally made 

 a too extensive application of schemes drawn from a number of observations. This 

 latter proceeding led indeed to more important mistakes in the hands of some 

 less careful followers. The task of critical examination could only be satis- 

 factorily performed after more profound investigation, aided especially by complete 

 experiments in artificial cultivation ; and this has resulted in showing that, owing to the 

 great number of the species, the differences in the course of development between 

 the homologous and analogous terminal points which are often very important, and 

 the frequent symbiotic relation social or otherwise between several species, the 

 complications may be much greater than would appear at first sight and than can be 

 expressed by one scheme. Various controversies also have arisen, as appears from 

 the case of Pleospora described above, out of all these labours and efforts which are 

 still far from their final conclusion. Much that belongs to this subject is only of 

 interest in connection with the individual cases and must be referred to in the descriptive 

 literature. We can here call attention only to the chief points of view, but it will be 

 well first of all to enumerate briefly the chief phenomena and members of the 

 development observed in the species above described. 



r. From the ascospore is developed a thallus which only produces asco- 

 genous sporocarps, or archicarps which produce these sporocarps together with 



