422 BOTANICAL.GAZETTE [DECEMBER 
variations is one of the best evidences of his familiarity with the sub- 
ject. Numerous writers ascribing to discontinuous variations the same 
importance he does to mutations have, as he says, regarded them as 
fundamentally distinct in the range of their deviation. Some of these 
writers have regarded their importance as a function of the extent to 
which they are aberrant. This question has been threshed over so 
thoroughly that I do not care to touch on it more than to suggest again 
the frequent sterility of sports. The assumed distinctness of discon- 
tinuous variations is, however, by no means so trite a subject. 
I disbelieve in the distinctness of these two classes of variations 
on empirical ground, and a priori. We will consider the former first. 
If they are distinct, it must be possible to draw a line between them, 
and to say positively of any variation with which we are thoroughly 
familiar that it is the one or the other, and to give a reason for the 
judgment. It will be classed as discontinuous only when the series of 
less considerable variations in the same direction breaks short of it. 
But every first-hand worker in this field knows that such series always 
tend to fill when the material is increased. In variation within wide 
limits or limits approximately but not absolutely fixed, the extremes 
of any finite number of examples are likely to be disconnected. When 
the number is increased sufficiently the gaps fill up, but new isolated 
extremes are found. Do the variations which are assimilated to the 
regular curve in this way thereby become continuous? If “discon- 
tinuous” means anything, they do; and if they do, it obviously does 
not mean very much. 
My abnormal ferns illustrate this assimilation of apparent mon- 
strosities into a regular series with the accumulation of enough 
material. The Polypodium I described from West Virginia, with the 
apical segment and its neighbors greatly enlarged, seemed most 
remarkable when I first collected it; but a thorough search of the spot 
the next season showed a long series of specimens bridging the g@P 
between these seeming monstrosities and typical plants. 1 have had 
the same experience with several lines of variation of P. calijornicum. 
In its extreme form the caudate monstrosity, with the frond as a whole 
narrowly oblanceolate, the individual segments abnormally broad and 
widening toward the round or retuse apex, and the midrib springing 
as a long curved hair from the dorsal surface, is the most extreme 
