I'."'' SUMMARY OF CUBRENT RESEARCHES RELATING TO 



In ;i specimen which bears a number of fine ovulate cells, with seed- 

 bodies approximately the same size as in the original Bmnettites 

 Gibsoniamis, the author found large angular to rounded pro-embryonal 

 cells. These appear to fill the entire nucellar space in some of" the 

 transverse sections. In others the pro-embryo cells appear to have been 

 but partially preserved or else to have collapsed, carrying the nucellar 

 wall inwards, as if there had been a central cavity in the large-celled 

 mass ; several irregular ribbon-like traces were also noted, about the 

 thickness of the cell-walls, extending across the large-celled mass. 

 These are not supposed to be suspensors, or tubular oospores or cells, 

 such as precede embryo-formation in Ephedra. Some sections suggest 

 that the mass of pro-embryo tissue was either less dense in its central 

 regions or that there was a small central cavity, but this point, which 

 would show a fundamental agreement with existing Cycads, cannot be 

 readily settled in absence of a good longitudinal section. It is evident, 

 however, that the lower half of the nucellus was closely filled by the 

 typical large undifferentiated cells making up the mass of the pro- 

 embryo. Another section showed the upper end of the nucellus ex- 

 tending well into the top of the seed, which is quite filled with the 

 characteristic tissue. 



There is no distinct indication of endosperm, or of differentiation 

 into an inner and outer zone. The pro-embryo tissue appears to be 

 homogeneous throughout, except in one instance, where some more 

 elongated cells appear to rest against the nucellar wall. 



Comparison with the other gymnosperms shows that the pro-embryo 

 of the Bennettitea3 is unique in occupying the entire nucellus, though it 

 must be borne in mind that the nucellse of the existing Cycads are 

 almost of the same size, increase in the size of the seed having been 

 plainly bound up with endosperm development. It may be that a pro- 

 gressive reduction of endosperm has taken place in the Bennettiteai. 

 and was perhaps a cause of the disappearance of the group. The 

 pro-embryo shows most resemblance to that of Ginkgo, and proves that 

 the embryogeny of Ginkgo is the most primitive among existing 

 gymnosperms. 



Life History of Pinus.* — Margaret C. Ferguson gives a detailed 

 account of the results of her work on this subject, derived mainly from 

 a study of Pinus Strobus. The subject-matter falls under the headings : 

 microsporogenesis, the male gametophyte, macrosporogenesis, the 

 female gametophyte, and fertilisation and related phenomena. In 

 most species the archesporium is well developed before winter, but the 

 mother-cell stage is not reached till the next April, or in P. Strobus till 

 May. There is probably a qualitative reduction of chromatin during 

 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. The 

 author describes a feature hitherto overlooked, a partial wall lying within 

 the intine at the prothallial end of the spore. The generative cell is not 

 surrounded by a definite wall, and when its nucleus divides the two 



* Proc. Washington Acad. Sci.. vi. (1904) pp. 1-202 (24 pis.). See also Cham- 

 berlain in Bot. Gazette, xxxix. (1905) pp. 06-7. 



