4 Morphologie etc, — Varietäten, Descendenz, Hybriden. 



Saxton, W. T., Development of the Embryo in Pinus 

 pinaster, Soland, with some notes on the life history oi 

 the species in Cape Colon y. (South African Journ. Sc. VI. 2. 

 p. 52—59. ill. 1909.; 



Only two archgonia are usually found in the prothallus of 

 Pimis pinaster. The embryo penetrates the prothallus, in all proba- 

 bility, not mechanically, but by the secretion of an enzyme. The 

 embryo grows for a time by means of a true apical cell, which 

 later becomes replaced by a group of apical meristematic cells. 

 Karyokinetic activity is then transferred to the proximal end of the 

 embryo, and the first differentiation is between the root periblem 

 and the rest of the embryo, which later forms cotyledons, stem 

 apex, and plerome. The cotyledons are all exacüy equal, and 

 equivalent in origin. Agnes Arber (Cambridge). 



Stephens, E. L., Recent Progres in the study of the em- 

 bryosac of the Angiosperms. (New Phytologist. VIII. 9—10. 

 p. 377—387. 1909.) 



The paper opens with a review of the principal suggestions 

 which have been advanced to account for the homologies and pos- 

 sible origin of the Angiosperm embryosac. Special attention is 

 devoted to Pearson's recent work on Welwitschia, in which he 

 has discovered a process of endosperm formation which can be 

 closely paralleled with that seen in the Angiosperms. In the embryo- 

 sac of Welwitschia 3X1 the nuclei at the end of free nuclear division 

 are potential gametes. Some of them remain free, and can function 

 as gametes, but the majority fuse in groups of six to twenty to 

 form a number of primary endosperm nuclei, by whose division 

 the cellular endosperm is produced. Pearson suggests that the 

 endosperm of the primitive Angiosperm was homologous with that 

 of Welwitschia. This implies that the embryosac of the primitive 

 Angiosperm contained many free nuclei, all potential gametes, and 

 a large number of primary endosperm nuclei formed by the fusion 

 of those gametes. In the modern Angiosperm, reduction has taken 

 place, and free nuclear division ends, as a rule, at the third gene- 

 ration from the megaspore. The eight nuclei thus formed are all to 

 be regarded as potential or reduced gametes. Pearson suggests 

 that the triple fusion was adopted when the decrease in the number 

 of nuclei available for fusion, and hence the decrease in the amount 

 of endosperm formed, had decreased the efificiency of the endosperm 

 as a feeding tissue. 



The remainder of the paper is occupied by a discusion of the 

 Suggestion that in certain anomalous cases, and possibly in all 

 cases in which the mothercell becomes the embryo-sac directly, 

 the embryo-sac includes four megospores. The author concludes 

 that it is hardly possible to prove or disprove the theory on the 

 evidence at present available. Agnes Arber (Cambridge.) 



Murr, J., Rassenbildung durch Rückkreuzung. (Magyar bota- 

 nikai Lapok. VIII. 5/9. p. 211-215. 1909.) 



Den vom Verf. 1902 (deutsche bot. Monatsschrift) aufgestellten 

 Satz „Bei der Mischung von zwei oder 3 Elementen erweist es sich 

 als besonders förderlich, wenn eines dieser Elemente nur in gerin- 

 ger Quantität d. h. nur angedeutet vorhanden ist. Letzteres Ver- 



