LIFE HISTORY OF PINUS II 



was called to the smallness of the first nuclear figure following 

 fecundation in comparison with the size of the conjugating 

 nuclei. The germ-nucleus divided in its original position in the 

 egg, and the two nuclei passed towards the " organic" apex of 

 the archegonium. 



Belajeff (1893) worked out the development of the pollen 

 tube in Picea as a type of the AhietinccE. He found that the 

 generative cell divided while still within the pollen-grain and 

 gave rise to two sperm-cells which he figured as of the same size. 



Dixon (1894) traced the history of the pollen-grain and the 

 pollen-tube in Piniis sylvcstris from the middle of April to the 

 time of fertilization. He thought that the prothallial cell divided 

 towards the end of April to form a small stalk-cell and a larger 

 body-cell. The body-cell immediately divided into two cells of 

 almost equal size — the male sexual cells. The sperm-cells 

 moved into the pollen-tube followed by the nucleus of the stalk- 

 cell. Pollen-tubes were found to branch freely while in the 

 upper "brown" tissue of the nucellus but only one branch of 

 each tube was continued through the lower part of the nucellus. 

 He noted that the four nuclei, much of the protoplasm, and 

 considerable of the starch of the pollen-tube passed into the 

 oosphere. As a rule, eight chromosomes were found in the 

 nuclei of the female gametophyte. 



In giving an account of some work done by his students on 

 the Gymnosperms, Coulter (1897) reported that the work of 

 Dixon " was largely confirmed in the minutest detail " ; and in 

 1900 he figured the pollen-tube "in pines," when just above 

 the archegonium, showing two sperm-cells of equal size. Atkin_ 

 son (1898) stated that the sperm-mother-cell in Pinus divided 

 into two sperm-cells after having passed into the pollen-tube. 



Blackman's excellent treatise on fertilization and related 

 phenomena in Pinus sylvestris was published in 1898. Man y 

 details of development were most carefully worked out, but th e 

 facts recorded are not enumerated here, since they will be duly 

 considered in connection with the observations, as record ed 

 in the body of this paper, that have been made by the writer on 

 other species of pines. Since the appearance of Blackman's 

 monograph, a considerable literature dealing with various stages 



