[Vol. 2 

 344 ANNALS OF THE MISSOURI BOTANICAL GARDEN 



tion of the young ascus to form branches and further croziers 

 resulting in an increase of asci as shown to take place in 

 Pyronema confluens by Claussen ('12, p. 25, fig. 6, III). 



It has been suggested by some who regard the fusion in 

 the ascus as a second fusion of nuclei (Harper, '05; 

 Overton, '06) that if the synkaryophytic condition of the 

 terminal portion of the ascogenous hyphae in Pyronema, 

 and far back in those of Galactinia succosa (Maire, '03, '05), 

 could "work back until the Qgg cell was reached," an 

 apogamous condition might result similar to that in the 

 Hymenomycetes. Certainly those who have suggested this 

 theory have not thought far enough ahead, for how would 

 the univalent condition of the spore nucleus pass to the 

 bivalent condition of each nucleus prior to the paired {= quad- 

 rivalent) condition in the ascogenous hyphae of the next 

 generation unless this were preceded by a nuclear fusion. 

 Such a condition would not be apogamy. The quadrivalent 

 character of the fusion nucleus of the ascus, or of the syn- 

 karion in the ascogenous threads, demands two successive 

 nuclear fusions, if the triple division in the ascus brings 

 about the reduction of a quadrivalent nucleus to a univalent 

 one as maintained by the adherents of this theory. As to 

 such an apogamous condition being similar to that in the 

 Hymenomycetes it must be remembered that there are only 

 two divisions in the reduction process in the Hymenomycetes, 

 so that when two univalent nuclei become associated in cells 

 of the mycelium or basidiocarp the bivalent condition of these 

 cells is attained. 



In a very interesting and scholarly argument Harper ('05) 

 has attempted to explain the inclusion and fusion of two 

 nuclei in the young ascus on the basis of the nucleo-cytoplasmic 

 relation or balance in the cell. The abundance of food ma- 

 terial in the tips of the ascogenous hyphae inhibits cell wall 

 formation so that two nuclei are enclosed in one cell. Rapid 

 growth of the ascus and cytoplasm follows in order to balance 

 the relation of the latter with the nuclear mass. The fusion 

 of the nuclei and growth of the fusion nucleus again over- 

 balance the cytoplasm, which then by growth increases again 



