The Cytology of Primula kewensis and of other 
related Primula Hybrids. 
BY 
L. DIGBY. 
With Plates XLI-XLIV and two Figures in the Text. 
A T no time has the great problem of heredity, which involves such 
l far-reaching results, been more widely discussed or more diligently 
studied than at the present day. It is now realized that the possibility of 
an ultimate solution must entail the study of genetics combined with that 
of microscopical investigation, for it is within the cells that the factors 
reside which determine the morphological and physical character of the 
individual. 
Much work has been done on the cytology of hybrids, both on the 
animal and on the vegetable side, and in many cases it has been possible to 
compare the nuclei of the parents with those of the offspring. The appear- 
ance and general character of the cytoplasm have been observed, the number 
and form of the chromosomes and their method of pairing in the bivalent 
combination have been described. After consideration of these cytological 
facts, conflicting hypotheses have been put forward in explanation of the 
causes of their frequently sterile condition. At present many of the 
detailed results remain as uncoordinated data, though it may be confidently 
anticipated that they will, in the future, be united into an intelligible scheme. 
It is in the hope of adding another item to these communications that 
this piece of work has been undertaken. Having regard to the curious 
horticultural history of the hybrid Primula kewensis , it seemed that a record 
of its cytology might be of interest. The attempt has been repaid, as the 
nuclear phases are wonderfully clear and the numbers of the chromosomes 
so low as practically to eliminate all chance of error. Moreover, the origin 
of the bivalent chromosome is suggestively easy of interpretation, and may 
throw some light on this much-vexed question. 
Methods. 
The buds have been capricious as regards fixation, and unless it 
has been good, the nuclei take the stain diffusely. In those cases where 
fixing and staining have been successful, nothing can exceed the clear 
definition of the nuclear phases. Sharpness of detail is characteristic of 
this series of Primulas. 
[Annals of Botany, Vol. XXVI. No. CII. April, 1912.] 
» B b 
