Apogamy in Ferns . 187 
The chief points of interest brought out by the foregoing table are, 
firstly, the small size of the nuclei as compared with cells in polydactyla , 
Wills, and the reversed relation in the case of cristata ; secondly, the fact 
that whilst the cells of polydactyla , Wills, are larger than those of the 
corresponding variety of Dadds, the chromosomes of the latter are far 
more numerous. As regards the antherozoids, it was not easy to arrive 
at exact estimations, but we incline to place those of cristata as slightly 
larger than those of polydactyla , Dadds ; we were unable to get satisfactory 
measurements of the antherozoids of the other variety. The measurements 
of the cells of the leaves 1 did not, as will be seen, give concordant 
results. 
We may, for the moment, omit from our consideration the chromo- 
some characters as presented by cristata , since they are affected by 
conditions different from those that concern the two varieties of polydactyla . 
The general result of a comparison of these forms shows that in internal, 
just as in larger external characters, divergence from the type may affect 
individual features independently, and this is strikingly shown by the smaller 
number of chromosomes possessed by the cells of polydactyla , Wills, and the 
larger number exhibited by the variety of Dadds, when both are compared 
with the type. This independence, as has been seen, extends to other 
characters within this group, and its existence serves to correct any impression 
of rigid correlation of differences with any one variant (e. g. chromosome 
number) such as a study of the forms of A thyrium Filix-foemina alone 
might perhaps have suggested. 
It seems not unlikely that comparative investigations on somewhat 
similar lines might usefully be extended to groups of allied species of other 
alliances, and it would be especially interesting to obtain this information 
in respect of those congeries of forms known as sub-species, mutations, and 
the like, in the case of flowering plants. 
It is now necessary to consider the question of the chromosomes more 
in detail. 
It has already been stated, in dealing with the individual forms, that 
the actual numbers obtained in each case are to be taken only as averages, 
but that the countings themselves yielded a certain divergence from each 
other round the mean. We are disposed to regard this divergence as not 
entirely due to errors in estimation, but as in part, at any rate, repre- 
senting a real difference. It has previously been shown 2 that differences 
occur in plants which only contain so few chromosomes as to make it 
impossible that the differences in the numbers estimated could be attributed 
1 In the intercellular spaces of the leaves of each variety the well-known glands are of frequent 
occurrence. 
2 Farmer and Reeves, On the Occurrence of Centrospheres in Pellia epiphylla , Nees. Annals 
of Bot., vol. viii. Farmer and Shove, On the Structure and Development of the Somatic and Hetero- 
type Chromosomes of Tradescantia virginica. Quart. Journ. Micr. Sci., vol. xlviii. 
P 
