70 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Bryophyta. 

 (By A. Gepp.) 



Phylogeny of the Archegoniatae and of the Characeae.* — H. 

 Schenck treats of the unsolved problem of the origin of the Arche- 

 goniatae. He discusses the commonly held view that in the green alga?, 

 and especially in Coleochcete, the ancestry of the Archegoniatae may be 

 sought, and the objections that weigh against this theory. Setting aside 

 the red algaB, as affording no clue, he passes on to a consideration of the 

 brown alga?, which have been already suggested by Potanie, Hallier, and 

 others. He points out that in Dictyota we find, for the first time 

 among the Thallophytes, the same form of regular alternation of genera- 

 tions which prevails in the Archegoniatae And by a comparison of the 

 reproductive organs, the author shows that the antheridia and archegonia 

 of the mosses and ferns are homologous with the plurilocular gametangia 

 of the brown alga3, and that the spore-mother-cells of the mosses and 

 ferns find their homologue in the tetrasporangia of Dictyota. In the 

 vegetative organs, also, are many indications of relationship between 

 the brown alga? and the Archegoniatae. Similar hints of a relationship 

 between the Characea? and the brown alga? are discernible. 



■.-' 



Reduction and Fertilisation in Polytrichum.f — J. and W. Docters 

 van Leeuwen-Reijnvaan describe the development of the sexual organs 

 in four common species of Polytrkhum, the double reduction that occurs 

 in the process, and the fertilisation of the egg by two antherozoids. In 

 the antherozoidal cell a small portion cut off from the nucleus passes out 

 into the cytoplasm and forms two centrosomes, and after the mitosis 

 becomes taken up again. A small piece of chromatin is cutoff, wanders 

 to the periphery of the cell, and becomes a blepharoplast. At the 

 same time a large piece of chromatin is cut off, extruded into the 

 cytoplasm, and gradually degenerates. In the sporogenous cells are seen 

 12 chromosomes : 4 long, 4 short, 4 medium. In the gametophyte are 

 found 6 chromosomes : 2 long, 2 short, 2 medium. Owing to a longi- 

 tudinal fusion in pairs, the chromosomes in the antherozoids are reduced 

 to 3 : 1 long, 1 short, 1 medium. The central cell and the ventral 

 canal cell of the archegonium each contain 3 chromosomes : 1 long, 

 1 short, 1 medium. These two cells fuse together, and the resulting 

 egg is fertilised by two sperms. It thereupon contains 12 chromo- 

 somes. The authors consider that the individuality of the chromosomes 

 is especially clearly indicated in Polytrkhum. 



The same authors % publish another paper, which treats of the sperma- 

 togenesis of mosses, with special reference to questions of centrosomes 

 and reductions in nuclear division. The material investigated for 

 centrosomes was Pellia, while the reduction of chromosomes was studied 

 in Polytrkhum and Mnium. 



Sexual Differentiation in the Spores of Fegatella.§ — A. F. Blakeslee 

 gives an account of some experiments, which demonstrate that the 

 sporogonium of the dioicous hepatic Fegatella produces both male and 



* Engler's Bot. Jahrb., xlii. (1908) pp. 1-37. 

 t Rev. Trav. Bot. Neerland, iv. (1908) pp. 177-220 (2 pis.). 

 t Ber. Deutsch. Bot. Gesell., xxvia. (1908) pp. 301-9. 

 § Bot. Gaz., xlvi. (1908) pp. 384-5. 



