6io MOSSES AND FERNS 



P. 23. Recent studies on Targionia (Deutsch (i) ), (O'Keefe (i) ) 

 have shown the presence of a single apical cell, and it is by no means 

 unlikely that this will prove to be the case generally in the Marchan- 

 tiales. 



P. 25. Barnes (2), after an examination of a number of Marchan- 

 tiales, states that invariably the formation of the air-chambers 

 begins by the separation of the cells below the superficial layer, and 

 thus the pits between the latter are secondary, being formed by a 

 splitting of the cell- wall. He* examined only Riccia natans and R. 

 fluitans, neither of which conforms to the type found in most ter- 

 restrial species. The papers by Miss Hirsch (i) and Miss O'Keefe 

 (i) show that Leitgeb's account of the formation of the air spaces in 

 Riccia glauca, and other allied species, is entirely correct. 



P. 32. The spermatogenesis in Riccia Frostii has been studied 

 in detail by Miss Black (i). It corresponds closely with that of other 

 Marchantiaceas. The final division of the sperm-cells is a diagonal 

 one without the formation of a division wall, and results in a pair of 

 triangular spermatids. There is no evident connection between 

 blepharoplast and a polar granule that might be considered to be a 

 centrosome. Eight chromosomes were noted in the sperm-nucleus. 



P. 35. Beer (i) has made a critical study of the spore division in 

 Riccia glauca. His results agree entirely with the writer's studies in 

 this species, and in R. trichocarpa, so far as the details were examined. 

 In both of these species, the spore mother cells, previous to the final 

 division into the spores, completely fill the cavity of the sporogonium. 

 The walls between them are very delicate, but are readily demonstrable 

 by Bismarck-brown. The protoplasts are usually more or less con- 

 tracted in microtome sections, and where the division walls are not 

 stained, look as if they were completely isolated, but probably in 

 most cases the contraction is due in part to the effect of reagents. 



Beer states that the division walls do not show the cellulose 

 reaction. Sooner or later these walls become disintegrated and the 

 nearly globular protoplasts, which have developed new membranes, 

 become entirely isolated. No evidence of any intercellular nutritive 

 substance, such as Garber (i) and Lewis (i) describe in R. natans, 

 can be demonstrated for either R. glauca or R. trichocarpa. 



The nucleus of the spore mother cell contains a conspicuous deeply 

 staining body (see text. Figs. 6, 7), which Beer states is a nucleolus ; 

 but from his description and figures of the early stages of mitosis it 

 looks as if this might be really composed of the closely united chromo- 

 somes. The latter, according to Beer, are probably seven or eight in 



