Dixon — On the Chromosomes of Lilium longiflonim. 717 



development of tte oosphere. And while the division of the nucleus 

 of the pollen-mother-cells and the primary nucleus of the embryo-sac 

 may very possibly conform to Professor Hacker's ' scheme, designed to 

 illustrate the formation of the first polar body; yet there is probably 

 nothing in the succeeding divisions which could correspond to his 

 scheme of the distribution of the chromosomes between the egg-nucleus 

 and second polar body, for in all the later divisions observed the noiTaal 

 longitudinal fission of the chromosomes occurred at the equator. 



The variation of number of nuclear segments found in the dividing 

 nuclei of the vegetative cells and in the divisions which take place, 

 prior to the formation of the pollen-grains in the pollen-sacs, is also 

 found in the mitoses which occur in the embryo-sac. As is well 

 known from Guignard's and Overton's researches, the upper nuclei of 

 the embryo-sac possess a smaller number of chromosomes than the 

 lower ; this disparity in number is veiy plainly seen in the mitoses 

 taking place in the embryo-sac of Lilium longiflorum. But what is of 

 special interest in the present case is the fact that the number of 

 chromosomes found in the upper nucleus of one embryo-sac, is not 

 always the same as that found in another embryo-sac taken from the 

 same ovary; one may possess twelve, the other only eight. In three 

 or four cases the number of chromosomes in this nucleus was found to 

 be ten. In these embryo-sacs the number of chromosomes in the 

 lower nuclei was usually, in those cases where it could be made out 

 with certainty, twenty-four, but also sixteen occurred. In the 

 subsequent divisions to form the four nuclei at the upper and the four 

 at the lower end of the embryo-sac, the upper nuclei were found to 

 possess eight to twelve nuclei, and the lower twenty -four or sixteen, 

 with occasionally intermediate numbers. 



So far as I am aware variations in the number of the chromosomes 

 have not before been found, and pointed out as occurring in the game- 

 tophyte of flowering plants prior to the differentiation of the sexual 

 cells. Strasburger and Guignard first showed that the number in the 

 nuclei of the endosperm of lilies was variable, and I myself found that 

 the nuclei in the endosperm of Pinus sylvestris differed from one another 

 in the number of their chromosomes. Again, Strasburger notices, 

 apparently as an anomaly, that he found some pollen-mother-cells of 

 Chlorophjton sternherffiaiiun,^ which, contained fourteen, while the normal 

 number of chromosomes in that plant is twelve. More recently Farmer^ 



^ Ann. of Bot., ix., xxxiii., 1895. ^ Kern- und Zelltheilung, p. 49. 



2 Ann. Bot., vol. ix. p. 488, September, 1895. 



