THE FUNGI : ASCOMYCETES AND BASIDIOMYCETES 293 



The cell (c.i) divides into two cells (d) and (e), which are surrounded by 

 cells of the perithecial wall. Cell (d) divides into two (d.i) and (d.z). In 

 this way a row of four cells are formed, which, starting from the tip, are 

 termed respectively the trichogyne (^.i), the trichophoric cell {d.2), the 

 ascogonium (e), and the stalk cell (^.i), which then divides again into 

 two cells (.?.i.i) and {s.1.2). 



The development of this sexual apparatus now continues by the elonga- 

 tion of the tip of the trichogyne, forming a receptive part at the top, beset 

 with numerous small swellings to which the spermatia become attached. 

 Though the details of the process of fertilization have not been observed, it 

 is concluded that at least one nucleus from a spermatium passes into the 

 trichogyne and makes its way down towards the functional female nucleus 

 situated in the ascogonium, for shortly after the final development of the 

 ascogonium the trichogyne withers and disappears. The further development 

 of the ascogonium consists in the cutting off 

 of two subsidiary cells, one above (e.i) and 

 one below {e.2). 



The fusion of nuclei in the ascogonium 

 transforms the ascogonium into a zygote and 

 stimulates the zygote cell (s) to divide into 

 four cells, two of which (z.i) and {s.2) are 

 shown ; while at the same time cell {d.2) 

 becomes narrower, due to the division of 

 the cells of the perithecial wall, which now 

 becomes two layers thick, and a second sup- 

 porting cell {e.2.i) is also formed by the 

 division of {e.2). 



The four cells (0.1), (^.2), {s.^), {s.4.) 

 now function as ascogenous hyphae, in 

 so far as each produces a row of four asci, 

 e.g. {z.2.1), (s.2.2), {z.2.2) and (^.2.4). In 

 each ascus eight nuclei are formed during 

 which presumably a meiosis occurs. In some 

 genera an ascospore is constituted around 

 each nucleus, but in Stigmatomyces baeri 

 and most genera, four of these nuclei abort 

 and only four spores are produced, e.g. 

 {z.2.2.1), {z.2.2.2), (3:.2.2.3), {z.2.2.At). 



By pressure of these developing asci the cells (e.1.2) and {e.2.1) together 

 with the cells of the inner perithecial wall {w.i) and (w.2) become dis- 

 organized and destroyed, along with the ascus wall, with the result that the 

 ascospores come to lie freely in the perithecial cavity. They are finally 

 liberated between the cells at the apex of the perithecium (r.i) and (r.2), 

 while the inner cells {t.i) and (^2) are destroyed. 



Fig. 286. — ■Chitouomyces paradoxus. 

 Entire plant with branch on 

 left terminating in mature 

 perithecium and branched 

 appendages arising from the 

 receptacle. 

 {From a photograph by Professor Weston.) 



