On the Cytological Features exhibited by certain 
Varietal and Hybrid Ferns. 
BY 
J. BRETLAND FARMER, F.R.S., 
AND 
L. DIGBY. 
With Plates XVI-XVIII. 
T HE last few years have witnessed the publication of the results of 
a number of investigations on the cytology of hybrid plants, and 
far-reaching inferences as to the significance of the chromosomes have been 
drawn from them. But the views of different investigators are somewhat 
widely divergent. Some have concluded that the frequent sterility of the 
hybrid is the result of an incompatibility between the parental chromosomes 
which enter into the nuclear constitution of the hybrid, whilst others, 
notably Tischler, 1 seem to attribute the failure of the reproductive processes 
to a disturbance of the normal relations of nucleus and cytoplasm. 
This latter conclusion is in harmony with the views advanced by 
R. Hertwig, according to whom the individual chromosomes are of com¬ 
paratively little significance, whilst the matter of supreme importance 
consists in the maintenance of certain definite relations between the nucleus 
and the cytoplasm which he embodied in his well-known formula K/P. 
The recent work of Popoff, 2 as well as the very valuable results 
obtained in earlier years by Klebs, 3 also points to the need of keeping 
in mind the mutual relations of nucleus and cytoplasm which have been too 
much ignored by some writers. We have seen no reason for departing 
from the position already taken up by one of us in 1905 4 to the effect that 
whilst the cytoplasm chiefly supplies the raw material for development, and 
1 Tischler, G., Zellstudien an sterilen Bastardpflanzen. Arch. f. Zellforschung, Bd. i. 
2 Popoff, M., Experimentelle Zellstudien. Arch. f. Zellforsch., Bd. i. 
3 Klebs, G., Die Bedingungen der Fortpflanzung, 1896, and other papers by the same author. 
4 Farmer, J. B., and Moore, J. E. S., Quart. Journ. Micr. Sci., xlviii, 1905, p. 553. 
[Annals of Botany, Vol. XXIV. No. XCIII. January, iqio.] 
