376 Digby. — The Cytology of Primula kewensis 
as they protrude and stretch to the periphery of the nucleus a limiting nuclear 
membrane appears (Fig. i o i) ; gradually each chromosome lies independently, 
as a rounded mass of homogeneous chromatin, in the nuclear cavity (Fig. 102). 
In a polar view of this stage 18 chromosomes have again been counted. A 
definite cloudy band, indicating the position of the future cell-wall, stretches 
across the equator of the fast disappearing spindle (Fig. 102). The next 
stage shows the longitudinal fission of the chromosomes preparatory for the 
homotype division (Fig. 103); again 18 chromosomes can be counted. 
There is nothing remarkable about the homotype division ; it is normal in 
every way. 
The pollen-grains are larger than those of P . floribunda > and approxi- 
mate in size to those of P. verticillata. 
The embryo-sac has been examined, and the embryo-sac mother-cell 
nuclei show 18 bivalent chromosomes (Fig. 106). There is no indication of 
the adherence of two bivalent chromosomes ; apparently this peculiarity is 
only characteristic of the heterotype division of the pollen mother-nuclei. 
At diakinesis (Fig. 104), in the profile (Fig. 105), and in the polar (Fig. 106) 
views of equatorial plates all the bivalent chromosomes are of the same 
size and are independent of one another. 
P. kewensis farinosa. 
It has already been mentioned that P. kewensis farinosa has arisen 
from two sources : in the one case as a variety of the fertile P. kewensis , in 
the other as the direct result of a cross between P. verticillata and P.flori- 
bunda isabellina ( 29 ), and both have doubled the number of the parental 
chromosomes. 
The meiotic phase of P. kewensis farinosa obtained by Messrs. Veitch 
from selection of P. kewensis (seedling) has only been studied with the 
view of ascertaining the number of the chromosomes, and these without any 
doubt are 36 and 18 (Fig. 107). 
The buds procured from the P. kewensis farinosa hybrid at Kew were 
young and had not as yet entered upon meiosis, but the somatic and arche- 
sporial divisions showed clearly that their chromosomes numbered 36 
(Fig. 108). 
Therefore O. gigas, whether it arises as a mutant or as a hybrid, and 
P. kewensis farinosa , whether it arises indirectly or directly as a hybrid, 
have both in each case doubled the parental number of chromosomes. 
P. verticillata x P. floribunda. 
The result of the cross between P . verticillata and P . floribunda ( 29 ) 
is a hybrid which repeats the number of the parental chromosomes, 18 (yx) 
and 9 (x), and resembles the seed parent, P. verticillata . 
