HOMOTYPOSIS IN THE YEC4ETABLE KINGDOM. 
.329 
We see from the last table how the “ hump ” disappears from the frequency dis¬ 
tribution when we exclude the fronds without son. The double mode indicates at 
least considerable flatness at the top of the distribution, and may possibly mark 
some heterogeneity of material. I am inclined, however, to think that tlie great 
variability (about forty-two even when the fronds without son are excluded) is fully 
accounted for by the sensitiveness of tlie fern in the matter of sari to very slight 
differences of environment. I look upon the high resemblance of like })arts here as 
having been intensified by this cause ; upon an inherent individuality we have super¬ 
posed an individuality due partially, perhaps, to age, but largely to small differences 
of immediate environment. Although the variation in the race is so lai’ge, and the 
degree of individuality so great, the ratio of individual to racial variability is still 
78 per cent. Thus while the variability of the hartstongue (as far as sori is concerned) 
is double that of the very variable holly, and almost thrice that of the poppy, still 
the percentage variability of the two latter sj^ecies is to that of the former only as 
about 85 to 78. Thus in the most variable and mo.st individual species we have yet 
come across, we still find the variation within the individual is more than three-fourths 
of the entire variation of the race. In view of facts like this, it seems impossible to 
maintain the position taken iq^ by Mr. Adam Sedgwick, that variation is the outcome 
of bi-sexual reproduction. The source of variation exists within the individual and 
is extensively active without the occurrence of any form of mating whatever. 
I place here the table for the distribution of soi i in pairs of fronds. The numbers 
in brackets are those which must replace the unbracketed numbers, if fronds without 
sori be excluded. 
VOL. cxcvir.— -A 
