i4 
Agnes Robertson. 
daughter-nucleus in typical cell-division, the very special 
mechanism for reducing the number of chromosomes during the 
maturation divisions, and the fact that as far as can be determined the 
sperm and egg nuclei at the time of fusion contain the same amount of 
chromatin, all strengthen the presumption that with the chromo¬ 
somes is associated the power of transmitting hereditary characters 
from one generation to another. 
Some support for the view that the chromosomes retain their 
individuality during the resting period is afforded by the fact that 
immediately before division they are often orientated about a pole, 
corresponding in position to the pole towards which in the previous 
division the chromosomes of the daughter nucleus passed. 1 If the 
chromosomes really retain their individuality, however often the 
nucleus divides, and if, further, there is not at fertilisation (as recent 
work seems to suggest) any actual fusion of chromosomes, it follows 
that the chromosomes derived from the male and female parent 
must exist side by side in the nucleus throughout the development 
of the plant! Blackman 2 says “ all the cytological work of recent 
years tends to show that the chromosomes have a distinct 
‘ individuality,’and the nuclei of the cells of the higher animals 
and the nuclei of the sporophytic cells of the higher plants are really 
dual in nature, there being no real mixing of the chromatin from 
the two sources until the time of chromosome-reduction.” There 
is a certain amount of evidence to shew that at least in some cases 
not only do the chromosomes retain their individuality throughout 
the development, but the whole male and female spiremes exist, at 
least for a time, separately in the fusion nucleus and the nuclei 
resulting from its divisions. Miss Ferguson 3 has shewn that in 
Finns strobus two separate spiremes can be recognised in the third 
division of the egg. Strasburger however will not allow that there 
is any reason to suppose that in ordinary plants the male and 
female spiremes persist separately throughout the sporophyte. He 
refers to the remarkable case of the Uredineae‘ where a process 
occurs which is apparently an extremely reduced form of fertilisation. 
An ordinary vegetative cell in the tissue close to the female cell 
functions as the male cell, and its nucleus enters the female cell. 
The two nuclei do not fuse, but persist separately through the 
■ E. Strasburger. l.c. 
' V. H. Blackman. “On the Fertilisation, Alternation of Genera¬ 
tions, and General Cytology of the Uredineze,” Annals of 
Botany, Vol. XVIII., 1904. 
* M. C. Ferguson. Proc. Wash. Acad. Sci., Vol. VI., 1904. 
* V. H. Blackman, l.c. 
