ICO 



FIRST GROUP. --THALLOPHYTES. 



4. ASCOMYCETES 1 . 



The Ascomycetes are an extensive group of plants of very complex structure, 

 whose specific peculiarities will be further discussed below. They are as a group dis- 

 tinguished by having their spores formed in asci, that is, the spores are in most cases 

 developed from the protoplasmic contents of club-shaped tubes or globular sacs. In 

 their simpler forms they have some resemblance through the formation of their fruc- 

 tification to the series of the Peronosporeae. If we take, for instance, the formation 

 of fructification in Podosphaera, we see two small lateral branches spring from the 

 place where two filaments of the mycelium cross each other, one forming an ellipsoid 

 cell which is separated off from its mycelium by a transverse septum (Fig. 63, w), and 



FIG. 62. Peziza (Pyronema) coiifluens. a small fragment of the hymenium, with / a paraphysis and three young 

 asci, m. r TV full grown asci, the order of development according to the letters ; in r the nucleus still undivided, in 

 s two nuclei formed by division of the inner nucleus, in u and v further multiplication of nuclei, lu ascuswith ripe spores. 

 After de Bary, magn. 390 times. 



the other a slenderer lateral branch from the other mycelial filament, which is closely 

 applied to the ellipsoid cell and a small obtuse cell cut off by a septum close beneath 

 its summit (Fig. 63, m). The further development shows what is in itself obvious, 

 namely that these organs bear the greatest resemblance to those which make their ap- 

 pearance in the sexual reproduction of the Peronosporeae ; the slender branch answers 

 to the antheridial branch there, the cell separated off at its extremity to the antheridium, 

 the broader ellipsoid cell to the female organ, the oogonium. The branch of the 

 thallus that corresponds to the oogonium (Fig. 63, w) is named by De Bary 2 , for 

 reasons to be discussed presently, the archicarp (ascogone); the antheridium, or 



1 [De Bary, Vergl. Morphol. u. Biol. d. Pilze, Myceotozven, u. Bacterien, Leipzig, 1884.] 



2 Beitr. z. Morphol. u. Physiol. der Pilze, Heft. IV. 



