REPRODUCTION IN DISCOLICHENS 163 



original cell nucleus. In the same cell, lying close against the lower septum 

 and partly within the opening, there was a mass of chromatin material which 

 might be the male nucleus migrating downwards. The next point of interest 

 was observed in the twelfth cell from the tip in which there were two nuclei, 

 a larger and a smaller, the latter judged to be the male cell, the small size 

 being due to probable division of the spermatium nucleus either before or 

 after leaving the spermatium. It is stated however that the spermatium 

 was always uninucleate. Meanwhile the cells of the ascogonium had 

 increased in size, the perforations of the septa between the cells became 

 more evident, and their nuclei persisted. In one cell at this stage two nuclei 

 were present, one of the two presumably a male nucleus; no fusion of nuclei 

 was observed in the ascogonial cells. Later the cross walls between the 

 cells were seen to have disappeared more completely and migration of 

 nuclei had taken place, so that some of the cells appeared to be empty while 

 others were multinucleate. Considerable multiplication of the nuclei occurred 

 before the ascogenous hyphae were formed : twelve nuclei were observed in 

 a part of the ascogonium which was just beginning to give off a branch. 

 Several branches might arise from one cell, and their cells were either uni- 

 or binucleate, the nuclei being larger than those of the vegetative hyphae. 

 The formation of the asci was not distinctly seen, but young binucleate 

 asci were not uncommon. The fusion of the two nuclei was followed by 

 the enlargement of the ascus and the subsequent nuclear division for spore 

 formation. In the first heterotypic division twelve chromosomes, double the 

 number observed in the vegetative nucleus, were counted on the equatorial 

 plate. In the third division they were reduced to the normal number of six, 

 from which F. Bachmann concludes that a twofold fusion must have taken 

 place in the ascogonium and again in the ascus. 



Spiral or coiled ascogonia were observed by Wainio 1 in the gelatinous 

 crustaceous genus Pyrenopsis, but the trichogynes did not reach the surface. 

 In Lichina?, a maritime gelatinous lichen where the carpogonia occur in 

 groups, trichogynes have not been demonstrated. 



A peculiarity of some gelatinous lichens noted by Stahl 3 and others in 

 species of Pkysma, and by Forssell 4 in Pyrenopsis and Psorotichia, is the 

 development of carpogonia at the base of, and within the perithecial walls 

 of old spermogonia. No special significance is however attached to this 

 phenomenon, and it is interesting to note that a similar growth was observed 

 by Zukal 5 in a pyrenomycetous fungus, Pleospora collematum, a harmless 

 parasite on Physma compactum and other Collemaceae. The structures in- 

 vaded were true pycnidia of the fungus as the minute spores were seen to 

 germinate. A " Woronin's hypha " at the base of several of these pycnidia 

 developed asci which pushed up among the spent sporophores. 



1 Wainio i. 1890. 2 Wolff 1905. 3 Stahl 1877. 4 Forssell 18852. B Zukal 1887, p. 42. 



II 2 



