CURRENT LITERAEUSE. 
BOOK REVIEWS. 
The life history of Pinus. 
Dr. FERGuson’s detailed account of this subject, profusely illustrated with 
excellent figures, will be useful as a reference work.* Much of the text and many 
of the figures have been taken from her previous papers, but the investigations 
have been pushed farther in every direction, so that the repetition adds to the 
value of the present account. The work deals primarily with Pinus Strobus, 
but conclusions are in most cases supported by observations upon several other 
species. 
winter, but the mother-cell stage is not reached until the following April; in P. 
- Strobus the archesporium does not appear until May. Probably there is a quali- 
tative 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. A partial wall, lying within the intine at the prothallial end of the spore, 
is an interesting feature not hitherto described. The body cell (“‘generative 
cell’) is not surrounded by a definite 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 two thousand free nuclei before walls begin 
to be formed. The archegonia appear about two weeks before fertilization. The 
independence of the male and female chromatin during fertilization, described 
by Miss Fercuson 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 rl nuclei, which lie in the cytoplasm of the main body of the egg. 
$s FERGusON’s conclusions are based upon an adequate field study and 
upon ae examination of an immense number of preparations, so that the danger 
eee ee ee dies a 
t FERGUSON, MARGARET C., Contributions to the life history of Pinus, with 
special reference to sporogenesis, the lpr eee of the gametophytes, and fertili- 
zation. Proc. Wash. Acad. Sci. 6:1-202. pls. I-24. 1904. 
1905] fi 
