and of other i r elated Primula Hybrids. 359 
During the summer of 1900, in order to verify the supposition that 
P. floribunda and P. verticillata were in fact the parents of P. kewensis , the 
cross was successfully achieved artificially, using P. floribunda as the seed 
parent and P. verticillata as the pollen parent. A proportion of the result- 
ing plants were true P. kewensis (29). The hybrid was sterile ; all its 
flowers were thrum- eyed, and hence the stock could only be increased 
by cuttings or division. 
In 1901 most of the sterile stock of P. kewensis passed into the hands 
of Messrs. Veitch and Sons of Chelsea. There it continued to bear only 
thrum-eyed flowers, until, aboutT905, a single pin-eyed flower was noticed. 
This flower was fertilized with the pollen of a thrum-eyed flower and 
good seeds were set. These germinated, and the resultant plants bore both 
pin-eyed and thrum-eyed flowers and were fertile. Thus the whole present- 
day stock of the seedling or fertile P . kewensis has originated from the 
single pin-eyed flower on the type or sterile P. kewensis . Messrs. Veitch 
have since produced by selection, not by cross-breeding, a varietal form, 
which they have named P. kewensis farinosa. This resembles the fertile 
P. kewensis , except that it possesses the pronounced mealiness of the leaves, 
calyx, and corolla so characteristic of P. verticillata. 
The cross between P. floribunda and P. verticillata has again been 
repeated at Kew by Mr. J. Coutts, the foreman, in 1910 (29), but this time 
the offspring resembles the seed parent P . floribunda, and not a single plant 
of P. kewensis has appeared. On the other hand, P. verticillata crossed 
with P . floribunda isabellina has given rise to plants resembling P. kezvensis 
farinosa , and, as will be observed, the interest is further enhanced by the fact 
that the number of chromosomes in this hybrid coincides with that of the 
plants of P. kewensis farinosa which were obtained by selection from 
P. kewensis (seedling form). 
Such is the horticultural history of P. kewensis . It is now necessary 
to compare the chromosome numbers in the various generations. 
Chromosome Numbers in the Primula Generations. 
Both parents, P. floribunda and P. verticillata^hdive. 18 for their diploid 
and 9 for their haploid number of chromosomes. These numbers, as might 
be expected, are repeated in the hybrid P. kewensis (type). 
The fertile (seedling) P. kewensis has, however, by some means doubled 
the number of chromosomes, and possesses 36 for its diploid and 18 for its 
haploid number. These numbers are also retained in the varietal form 
P. kewensis farinosa , and again reappear in the P. kezvensis farinosa which 
has arisen at Kew (29) as the result of crossing P. verticillata with P. flori- 
bunda isabellina , the pale form of P . floribunda. 
Material of the fertile P. kewensis has been obtained from several 
B b % 
