f>4 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Reproductive. 



Embryology of Arissema.*— F. L. Pickett has studied the develop- 

 ment of the embryo-sac of Arissema triphyllum, and although most of 

 the results agree with those of previous investigators, the author has 

 discovered a few variations which have not been described before. 

 The origin of the mega«pore mother-cells from a single primary cell is 

 doubtful, the first division of the tetrad having probably been mistaken 

 for a division of a primary cell into embryo-sac initials. The tetrad is 

 composed of potential megaspores, some of which will develop into the 

 embrvo-sac or sacs. As in other Araceas, more than one embryo-sac 

 may lie formed. It is doubtful whether the polar nuclei ever fuse, 

 while the antipodal cells are rarely fully developed. 



Embryology of the Euphorbiacese.t — Gr. Donati has studied the 

 embryology of eight species of Euphorbiacese, and finds that in seven 

 of them the development is normal : in Poimettia pulcherrima, however, 

 the two embryo-sacs have each sixteen cells and nuclei. This is the 

 fourth instance of the kind in this family, and appears to indicate that 

 further investigations will reveal further abnormalities. 



Embryology of the Dianthacese.:}: — R. Perotti has studied specimens 

 of six different representatives of the Dianthaceae in order to determine 

 (1) the origin of the embryo-sac ; (2) the number of embryo-sac mother- 

 cells and of embryos in the nucellus ; (3) the origin and structure of the 

 large suspensor-cells found in Stellaria media and other species. The 

 author finds that in Stellaria media, Lychnis dioica, Silene Cucubalus, 

 Tunica prolifera, and Gypsophila saxifraya, the archesporial cell does not 

 develop directly into an embryo-sac, but undergoes a previous tangential 

 division. In these species the mother-cell arises from the lower cell and 

 in Cerastium glomeratum from the upper cell. In all six species there is 

 usually a complete tetrad-division, and the lowest cell forms the embryo- 

 sac. Silene Cucubalus frequently has a multicellular archesporium, 

 several embryo-sac mother cells, and several embryo-sacs. In Cerastium 

 glomeratum, Lychnis dioica, and Silene Cucubalus, the suspensor has a 

 bladder-like ceil of a haustorial nature similar to that found in Stellaria 

 media. In Tunica prolifera, Gypsophila saxifraya, and Sapouariu offici- 

 nalis, the adjacent cell is also much enlarged, while the remaining sus- 

 pensor cells are reduced both in size and number. 



Anatomy and Germination of Heteromorphous Seeds. § — H. Baar 

 has studied the anatomy and the physiology of the germination of 

 heteromorphous seeds of Chenopodium album and Atriplex nitens. The 

 difference in appearance of the seed is accompanied by difference in 

 structure ; this especially applies to the thickness of the seed-coat with 

 which is closely connected the capacity of the seed for absorption of 



* Bull. Torrey Bot. Club, xl. (1913) pp. 229-35 (2 pis.). 



t Zeitschr. Bot., v. (1913)p. 792. See also Annul di Bot., xi. (1913) pp. 395-9 

 (1 pi.). 



\ Zeitschr. Bot., v. (1913) pp. 792-3. See also Annal. di Bot., xi. (1913) pp. 

 371-85 (3 pis.). 



§ S.B. Akad. Wiss., exxii. (1913) pp. 21-40 (2 pis.). 



