308 THE LOWER FUNGI— PHYCOMYCETES 



either case they are multinucleate from the first and are morpho- 

 logically indistinguishable. They come in contact near their 

 tips and fuse, a wide opening resulting. The female cell (ascogo- 

 nium) then pushes out at its apex, and elongates to form a long 

 fiexuous tube which tapers to a slender termination. The male 

 cell (antheridium) does not increase in size, but retains its 

 identity, so that the elongated ascogonium seems at maturity 

 to have a forked base. The nuclei of the antheridium mingle 

 with those of the ascogonium, and one of the male nuclei fuses 

 with one of the female to form a single large fusion nucleus. 

 This fusion is figured by both Juel (1902 a; 1921) and Dangeard 

 (1907). Following fusion, repeated nuclear divison results finally 

 in a large number of small nuclei. These are distinguished with 

 difficulty from the supernumerary sexual nuclei. The latter 

 tend to sink toward the bottom of the cell, while the progeny 

 of the fusion nucleus retain their position in its upper end and 

 become the centers of uninucleate spores. The spores are accom- 

 panied by intersporal substance, and are said by Juel to be cut 

 out as in higher Ascomycetes by free cell formation. They are 

 termed ascospores, and the elongated ascogonium which bears 

 them is then called the ascus. It ruptures apically at maturity 

 and the spores are extruded in a mass through a definite pore. 

 They are globose to ellipsoidal, hyaUne, and smooth. 



The inclusion of Dipodascus in the Ascomycetes seems to be 

 completely justified by Juel's observations on stained material. 

 Though the ascogonium and ascus here are essentially the 

 same structure, and though ascogenous hyphae and ascus hooks, 

 common in higher Ascomycetes, are lacking, two features 

 typical of the ascus of the Euascomycetes are present. There is 

 a fusion of a single pair of sexual nuclei, and the spores are thought 

 to be delimited by the astral rays. The multispored character 

 of the ascus emphasized by Schroter is of little significance, 

 since this condition exists in various higher forms also. In an 

 interesting discussion of the phjdogeny of the Ascomycetes 

 Atkinson (1915) presents arguments supporting the hypothesis 

 that that group arose from phycomycetous ancestors through 

 forms such as Dipodascus. From this point of view D. alhidus is 

 the most primitive of all the known Ascomycetes, and may be 

 regarded as perhaps showing relationship with species of the 

 genus Endogone which is placed by various authors in the Muco- 

 rales (p. 265). The complete life cycle in the last named genus is 



