268 CLASS ASCOMYCETEAE 



nonfunctional antherid ("trophogone") around which the young ascogo- 

 nium coiled without uniting with it. (Fig. 89.) 



In Chaetomium kunzeanum Zopf and C. bostrychoides Zopf a cell of an 

 ascogonial coil is fertilized, according to Greis (1941), by an antherid at 

 the tip of a slender hypha arising near by or at some distance. A coil of 

 thick binucleate cells results. In the second species there grow up around 

 this coil, from below, the hyphae that produce the perithecial wall, while 

 other hyphae grow upward between the ascogenous hyphae arising from 

 the ascogonium, to form the paraphyses. The terminal cell of each as- 

 cogenous hypha becomes an ascus, without crozier development. In C. 

 kunzeanum the perithecium may develop in the foregoing manner, but 

 usually also there grows out from the thickened ascogonium a stout 

 creeping, branching extension, up to several centimeters in length, from 

 which arise, laterally, coils giving rise to ascogenous hyphae, typical 

 perithecia being formed around them. Thus from one act of fertilization 

 (cytogamy) there may arise, radiating from this point, up to 10 perithecia. 

 This is suggestive of the condition in the genus Dudresnaya in the Florid- 

 eae (Red Seaweeds). 



In Xylaria, in which numerous perithecia are produced in a stroma, 

 coiled ascogonial hyphae were observed by Brown (1913) in the stroma 

 at points where the future perithecia were due to arise, but their further 

 development has not been reported. Somewhat similar structures were 

 reported by Miss Lupo (1922) in Hypoxylon. 



Many of the Pyrenomycetes lend themselves readily to cultivation on 

 various media. In some cases cultures from single ascospores will produce 

 perithecia, but very often they have not been produced in such cultures. 

 Edgerton (1914) studied a strain of Glomerella cingidata (St.) Spaul. and 

 von Sch. in which a scattering development of perithecia was produced on 

 cultures from a single ascospore but yet when two such cultures were 

 allowed to grow in contact with each other a great mass of perithecia 

 appeared along the meeting line in about half the cases, i.e., when the 

 opposite sexual phases met. 



Miss Dowding (1931) and Ames (1932, 1934) have shown for Schizo- 

 thecium anserinum, as B. 0. Dodge (1927) had shown previously for 

 Neurospora tetrasperma Shear and Dodge, that the ascospores are usually 

 four in number and binucleate. From single spore cultures of such spores 

 perithecia are produced in abundance. Occasionally in place of a bi- 

 nucleate spore two uninucleate spores are produced. These, Ames has 

 shown, produce two mutually compatible and self- sterile mycelia while 

 the binucleate spores produce fertile mycelium, each type of mycelium 

 bearing both male and female organs. By cutting off and transplanting 

 hyphal tips containing one or a very few nuclei Ames determined that in 

 the mycelium from the binucleate spores there are two sorts of nuclei 



