LIFE HISTORY OF PINUS 5 



nard (1902), fertilization follows in 2 hours after pollination, but 

 in Phms, where almost 13 months intervene between these two 

 processes, such a number is not excessive. While it is true in 

 cytological studies, as elsewhere, that numbers, or mere mass 

 work, do not signify excellence, it is equally true that the re- 

 sults of investigations based upon a study of a limited amount 

 of material are, at best, unsatisfactory, and, other things being 

 equal, those conclusions will be most valuable which have been 

 formulated after a careful observation of many specimens.' 



HISTORICAL NOTES. 



In the following brief summary of the literature dealing 

 with the AbicttiiccB, only the more important papers have been 

 noted, and the observations recorded by the various writers 

 have been given without comment. 



The tetrad-division in the pollen-mother-cell of Pinns and 

 Abies was studied in 1848 by Hofmeister. He stated that the 

 pollen-mother-cells were already developed in the anthers at the 

 end of November, two special daughter-cells were formed at 

 the close of the first division in the spring, and the four cells 

 resulting from the second division were found to lie either in 

 one plane or at the corners of a tetrad. Three years later 

 (185 1) Hofmeister published the results of his remarkable series 

 of investigations in the higher cryptogams and conifers. He 

 described and figured the pollen-grain in the AbietinecB as con- 

 sisting of a cell-complex, noted the depression in the apex of 

 the nucellus in Piniis at the time of pollination, and the single 

 embryo-sac-mother-cell deep in the interior of the nucellus. It 

 appeared that the pollen-grain rested some weeks upon the 

 nucellus before the pollen-tube was emitted. After the germina- 

 tion of the pollen-grain, the tube grew for several weeks and 

 penetrated nearly to the point of union between integument and 

 nucellus, but it might cease growth before so great a depth was 

 reached. 



1 This paper was given especial honorable mention on April 26, 1903, by the 

 Association for Maintaining the American Women's Table at the Zoological 

 Station at Naples and for Promoting Scientific Research by Women. I wish here 

 to express my deep gratitude to Mrs. Ellen H. Richards, Miss Florence Gushing 

 and other members of the above named association through whose generous 

 efforts the publication of this paper in its present form has been made possible. 



