212 Cytologie und Befruchtung. — Descendenz und Hybriden. 



Ferguson, Margaret C, Contributions to the Life His- 

 t o r y o f Plnus with special reference to Sporo- 

 genesis, the Development of the Gametophytes 

 and Fertilization. (Proceedinsrs oi the Washington Acad. 

 of Sciences. Vol. VI. 1904. p. 1—202. Plates 1—24.) 



This is a detailed account of the life history of Plnus and 

 is profusely illustrated with excellent figures. Much of the text 

 and many of the figures have been taken from Dr. Ferguson's 

 earlier papers but the investigations have been extended in 

 every direction. Pinus strobus is the principal form studied 

 but conclusions have, in nearly all cases, been supported by 

 investigations upon several other species. The titles of the five 

 chapters are : microsporogenesis, the male gametophyte, macro- 

 sporogenesis, the female gametophyte, and fertilization related 

 phenomena. in the appendix several abnormal conditions are 

 described. 



In most species the archesporium is well developed before 

 the approach of winter but the mother-cell stage is not reached 

 until the following May; in P. strobus the archesporium does 

 not appear until May. The writer is inclined to beiieve that 

 a qualitative reduction of the chromatin occurs at the second 

 mitosis in the pollen mother-cell. The air sacs arise by the 

 Separation of the exine from the intine at two definite points. 

 A partial wall, lying v/ithin the intine at the back, or prothallial 

 end of the spore is an interesting feature not hitherto described. 

 The body cell („generative cell") is not surrounded by a defi- 

 nite wall and when its nucleus divides, the two sperm nuclei 

 lie free in a common mass of cytoplasm, never organizing 

 distinct sperm cells. The two sperm nuclei are unequal in 

 size and the larger one is always in advance. 



The endosperm contains about 2000 free nuclei before walls 

 begin to be formed. The archegonia appear two weeks before 

 fertilization. The independence of the male and female chro- 

 matin during fertilization — described by Dr. Ferguson and 

 previous investigators — is here worked out in great detail. No 

 cell walls are laid down at the base of the oosphere until the 

 eight nucleate stage of the proembryo has been reached. The 

 divisions which result in the formation of four tiers of cells in 

 the proembryo are described as taking place in the upper nuclei 

 which lie in the cytoplasm of the main body of the egg. 



A further study of the proembryo is in progress. 



Charles J. Chamberlain (Chicago). 



Caille, Note surdesformesdiametralement opposees 

 apparues sur un Chelidonium majus et un Ranunculus 

 aconitifolius. (Bull. Mus. d'Hist. nat. 1904. p. 403.) 



L'auteur Signale le cas d'un Chelidonium majus var. flore 

 pleno qui a perdu ses fleurs doubles et est revenu au type 



