Morphologie und Teratologie. 215 



are especiaily large. The other prothalli which develop do so more 

 slowly and form the „secondary prothalli". They contain 

 numerous nuclei in the cytoplasm but no formation of cell- 

 walls takes place. The superficial cells of the primary pro- 

 thallus grow out into processes and appear to derive nourish- 

 ment from the secondary prothalli. The archegonia arise from 

 a number of deeply situated cells of the primary prothallus. 

 After the primary neck cell has been cut off, the enlargement 

 of the central cell forces the neck to the surface of the pro- 

 thallus. Two, occasionally four, neck cells are formed. No 

 ventral canal cell is separated, but the nucleus of the central 

 cell divides and one of the resulting nuclei desintegrates, bearing 

 the egg-nucieus. The elongation of the enlarging archegonia 

 is always directed towards one of the pollen-tubes lying along- 

 side the embryo-sac. Two male cells arise in the pollen tube 

 by the division of the body-cell. They become piaced opposite 

 two archegonial necks. A narrow communication is establi- 

 shed with the archegonium and the male nucleus with a very 

 smail amount of cytoplasm escapes from the male-cell and enters 

 the ovum. Both male nuclei are functional and fertilise neigh- 

 bouring archegonia. The male and female nuclei are of equal 

 size and before fusion the former becomes partially surrounded 

 by the egg-nucleus. In the formation of the embryo no free 

 nucleus divisions occur. A row of four cells is formed and the 

 lowest of these divides into the suspensor cell and the embryo. 

 Lach fertilised ovum gives rise to a single embryo. Sofar as 

 could be estimated there were sixteen chromosomes in the cells 

 of the gametophyte and thirty-two in those of the sporophyte. 



W. H. Lang. 



LEDOUX, P., Sur la morphologie de la racine des plan- 

 te s ä emb ryo n m util e. (C. R. Acad. d. Sc. T. CXXXVIII. 

 13 Juin 1904. p. 1525.) 

 L'enlevement du point vegetatif de la radicuie ne permet 

 plus la regeneration de l'organe lese ; il provoque le developpe- 

 ment de radicelles plus fortes et plus nombreuses que sur les 

 germinations normales. La croissance subterminale de Taxe 

 principal y est partiellement remplacee par une croissance inter- 

 calaire puissante. Les radicelles de remplacement subissent une 

 action geotropique plus intense que les radicelles normales. 



Lignier (Caen). 



I, G., Contributo a 1 1 o studio d e i 1 a e t e r o f i 1 1 i a. 

 (N. Giorn. Bot. Ital. Vol. XL 1904. p. 186—234. Tav. I 

 e IL) 



L'auteur a etudie soigneusement les variations de la structure 

 anatomique des feuilles chez 19 plantes heterophylles qu'il 

 groupe, comme conclusions de son etude, parmi les 7 types prin- 

 cipaux suivantes: 



