Biologie. — Cytologie und Befruchtung. 483 



des Perianths führen die Staubgefässe eine freiwillige Auswärts- 

 bewegung aus. Eine freiwillige Einwärtsbewegung derselben 

 findet nicht statt, doch drückt das Perianth bei seiner Schliess- 

 bewegung die Staubgefässe dem Gynäceum derart an, dass der 

 zu dieser Zeit noch vorhandene Pollen Gelegenheit zu einer 

 zweiten Selbstbestäubung bekommt. Bei Spergularia rubra L. 

 kann sogar eine dreimalige Selbstbestäubung stattfinden; doch 

 werden die honigreichen Blüthen dieser Art an insektenreichen 

 Orten von zahlreichen Insecten besucht und bestäubt. Bei 

 Spergula arvensis L. ist im Sommer wohl Selbstbestäubung 

 die Regel, während im Frühling und Herbst die Blüthen reich- 

 licher besucht werden. Das Blühen der beiden genannten 

 Arten wird ausführlich geschildert. Büsgen (Hann. Münden). 



BlRR, Harriet C, The Embryology of Vallisneria spiralis. 

 (Ohio Naturalist. Vol. III. 1903. p. 439-443. PI. 19.) 



The pollen grain of Vallisneria, at the time of shedding, 

 contains two male cells and the tube nucleus. The embryo-sac 

 develops from the lowest of a row of four megaspores. The 

 two polar nuclei fuse near the center of the sac but no parti- 

 cipation of a male nucleus in this fusion was observed. The 

 development of the endosperm is about as in Sagittaria, except 

 that the large nucleus in the antipodal Chamber does not divide. 

 The development of the embryo follows quite closely that of 

 Sagittaria, as described by Schaffner. 



Charles J. Chamberlain (Chicago). 



COOK, M. T., Polyembrvony in Ginkgo. (Botanical Gazette. 

 Vol. XXXVI. 1903. p.' 142.) 



An examination of 200 seeds of Ginkgo gave the following 

 results: 12 per. cent. were without embryos, and 2 per. cent. 

 contained two embryos in each seed. In cases of poly- 

 embryony the two embryos were about equal in size and were 

 about two thirds the length of single embryos. 



Charles J. Chamberlain (Chicago). 



COOK, M. T., The Development of the Embryosac and 



Embryo of Agrostemma Githago. (Ohio Naturalist. Vol. III. 



1903. p. 365—369. PI. 7.) 



The embryo-sac of Agrostemma, which presents nothing 



unusual in its "development, comes from the lowest of a row of 



three megaspores. The nucellus soon shows two well defined 



zones, the outer of which grows very rapidly, so that the 



embryo-sac becomes deeply placed. The nucellus develops a 



prominent beak which projects through the micropyle. The 



embryo is at first filamentous, with the basal cell much enlar- 



ged. Calyptrogen, dermatogen, periblem and plerome are quite 



distinct at the root apex. Charles J. Chamberlain (Chieago). 



31* 



