ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 337 



American winter. But in the hybrid plants the strain of the American 

 parent confers immunity from the frost. 



Descriptions of New Tropical Ferns.*— E. Rosenstock gives descrip- 

 tions of ten new species of ferns from German East Africa, Brazil, 

 Uruguay, Ecuador, Sumatra, and indicates their affinities. 



New Species of Lindssea.j — L. M. Underwood and W. R. Maxon 

 describe two new species of Lindsma, one collected in Colombia by 

 Pittier, and the other in Cuba by Wright and other botanists. 



Ferns of Paraguay 4 — H- Christ publishes descriptions of some nine 

 new species of ferns collected in Paraguay by E. Hassler, and adds notes 

 upon two other rare species. 



Bryophyta. 



(By A. Gepp.) 



Sexuality in the Mosses.§ — J. Cardot treats of the question of 

 sexuality in the mosses, and gives a summary of the results obtained 

 by El. aud Em. Marchal. The Marchals investigated the life-history 

 of three dioicous mosses — Barbula unguiculata, Bryum argenteum, 

 Ceratodon parpareus — with a view to determining whether or not the 

 numerous plants arising from the spores of a given sporogonium, itself 

 the product of one and the same fertilised egg, are all of one sex. They 

 found them to be of different sexes. And, further, they ascertained 

 that the sex of the ultimate plant is already predetermined in the spore ; 

 that the protonema unfailingly transmits the sex of the spore to the 

 young plants — that is to say, that the protonema buds off plauts which 

 are solely male or solely female ; that a secondary or regenerative pro- 

 tonema is equally faithful in the transmission of sex. Hence dioicism 

 originates at the time of sporogenesis, at the time of the division of the 

 spore-mother-cells, when reduction of chromosomes takes place. 

 Previous to the time of this nuclear reduction all the cells of the 

 sporogonium (both stalk and capsule) possess a bisexual potentiality. 

 And when at this stage portions of the sporogonial wall or stalk are 

 made to regenerate as a consequence of traumatic injury, an aposporic 

 protonema is obtained. And the Marchals state that in case of the three 

 dioicous species — Bryum ccespiticium, B. argenteum, Mnium hornum — 

 the aposporic protonema produces gonophytes, which in the great 

 majority of cases have a male character, while some bear synoicous 

 flowers, and a few exhibit a female character only. But are the sexual 

 characters of these axes maintained by the products of their vegetative 

 reproduction ? Experiments instituted to settle this question have 

 brought out this important fact: that the products of the second diploid 

 generation are bisexual, whatever be the sex manifested by the axes of 

 first generation whence they arose ; these latter are then in every case 



* Fedde, Repertorium, iv. (1907) pp. 2-6, 292-6. 

 t Smithsonian Misc. Coll., 1. (1907) pp. 335-6. 

 % Bull. Herb. Boissier, ser. 2, vii. (1907) pp. 922-8. 

 § Rev. Bryolog., xxxv. (1908) pp. 8-11. 



June 17th, 1908 2 A 



