HOMOTYPOSIS IX THE VEGETABLE KINGDOM. 
327 
anticipated in accordance with it a fairly high correlation of nndifterentiated like 
organs, and this has, indeed, turned out to he the case. 
(17.) Somersetshire Hartstongue (Scolopendrium vulgare).—I owe the counting of 
the sort on 8 to 12 fronds of each of 101 hartstongue ferns to Miss Agxes Fry. It 
was not always possible to obtain the full suggested number of 10 fronds. In a few 
cases Miss Fry also counted more than 10. But the ferns with fewer than 10 are 
not many, and the distribution of the fronds is sensibly identical wa’th that of the 
pairs of fronds. The number of sori was often very large, running up to 180; the 
grouping of the leaves was accordingly arranged in units of 10 sori, and, to save 
fractionising in the table, these groups were taken 0—-O'S, 9’5—19’5, 19‘5—29'5, &c. 
The grouping on the basis of Miss Fry’s record was carried out by Mr. Leslie 
Bramley-Moore. With regard to the counting of the sori, all the sterile as well as 
the fertile markings were included. Fronds with no markings were included ; one 
plant, the only one found, with absolutely no markings on any of the fronds was 
excluded, and to this I shall recur immediately. It was difficult to procure ten perfect 
fronds ; many of those gathered were found to be more or less torn ; in many cases 
the loss of sori was easily ascertained ; in others an estimate had to he formed. Such 
estimates were made, however, in only forty-four cases out of more than 1,000 fronds, 
and in the majority of these cases it meant the addition of very few sori, and a possible 
error in the estimate of still fewer. Sometimes one or two sori may have been missed 
at the tip, where the small markings are indistinct, ])ut the errors due to this source 
as well as to the occasional error of a unit or two in counting such a large number 
are well under the unit of grouping of ten sori finally selected. The environment of 
the series was not cpiite uniform, some thirty-three coming from a stream bed and the 
remainder from a park glade. The plants varied considerably in age, hut the necessity 
of procuring eight to twelve fronds was probably eftective in excluding any quite young- 
ferns. The absence or presence of sori on the frond was not directly associated with 
its age or size. Miss Fry has recorded a number of large and medium fronds with 
no soii, and some (ffi the fronds recorded as young have occasionally a very con¬ 
siderable number of sori (as many as ninety-five on one at least). Still, a glance at 
the table on p. 330 shows that the fronds with zero sori form in same way an anoma¬ 
lous group ; they give a hump in the frequency distribution in a manner somewhat 
similar to that due to barren wives in fertility-frequency curves.^ Dr. Lee having 
tabulated the sori, and calculated the constants on the basis of including all fronds 
with zero number of sori, I went through Miss Fry’s data again and excluded, not 
all the entries in the first row and column of Miss Lee’s table, hut only such of 
them as arose from the fronds with no sori. The result was a great smootliing of 
the table, a raising of the mean, and a lowering of the varialiility ; hut no appreciable 
effect whcUever was made on the degree oj resemblance of like organs, although I 
* See ‘The Chances of Death and other Studies in Evolution,’ vol. 1, essay on “Eeproductive 
Selection,” and diagram. 
