19"] CURRENT LITERATURE 83 



the stem is strong evidence in support of the interpretation of the filling tissue 

 as peculiar outgrowths. Nothing comparable to such multicellular hairs on 

 roots has been found in present ferns, although it is possible that examination 

 of tropical tree ferns may reveal traces of similar structures. — Grace M. 

 Charles. 



The development of Pyronema confluens. — Believing that the alterna- 

 tion of generations has not yet been satisfactorily worked out in any fungus, 

 Claussen 21 has completed an extensive cytological and morphological study 

 of the development of Pyronema confluens, a form already investigated by 

 Harper 22 . The spores germinate immediately on being discharged from the 

 ascus. He finds that under favorable conditions any cell of the fungus may 

 develop into a complete plant. In material grown on agar at 20 C. in direct 

 sunlight, he finds that the vegetative mycelium is produced in 1-2 days; the 

 fruit bodies begin to form in 2-3 days; fertilization occurs in 3-4 days and the 

 first ascogenous hyphae appear; after 5 days the recurved tips of the ascogenous 

 hyphae are observable; young asci may be found on the sixth day, at which 

 time 1, 2, 4, and 8-spored asci are present. In cultures under these conditions 

 the fungus completes its development in 7-8 days. Claussen observed that 

 the younger stages of the fruit bodies often arise from dichotomously branched 

 aerial hyphae, so that they are often stalked. His observations as to the origin 

 of the sexual organs agree in general with the earlier descriptions of De Bary 2 * 

 and of Kjhlman. 2 ** The hyphae, which bear the ascogones, and those which 

 bear the antheridia, may arise from the same mycelial thread; the fungus, 

 therefore, is homothallic. 



The mycelium consists of multinucleate cells. Protoplasmic streaming 

 was observed in the hyphae, indicating that there is a pore in the cross-walls, 

 connecting the contents of adjacent cells. The hyphal branches which bear 

 the sexual organs are always multinucleate. Claussen is unable to determine 

 whether or not nuclear division occurs in the ascogone and in the antheridium 

 before fertilization. So far as he is able to discover, the nuclei in the sexual 

 organs are exactly alike. When the sex organs are mature, he observes that 

 the nuclei increase in size, but that there is a more marked increase in the size 

 of the nuclei of the ascogone. Certain nuclei in both male and female organs 

 degenerate before the sexual act. The phenomena concerned in the fusion of 

 the antheridium with the trichogyne, the passage of the male nuclei into the 



21 



Claussen, P., Zur Entwicklungsgeschichte der Ascomyceten. Pyronema 



confluens. Zeitschr. Bot. 4: 1-64. pis. 6. figs. 13. 1912. 



22 



Harper, R. A., Sexual reproduction in Pyronema confluens and the morphology 



of the ascocarp. Ann. Botany 14:321-400. 1905. 



23 De Bary, A., Ueber die Fruchtentwicklung der Ascomyceten. Leipzig. 1863. 

 34 Kihlman, O., Zur Entwicklungsgeschichte der Ascomyceten. Acta Soc. Scient. 



Fenn. 13:29-40. 1883. 



