measured, I have not thought it worth while to complicate the results by
giving separate averages for them and for the pairs, but have added up
all their heights, and thus obtained a single average.

I long doubted whether it was worth while to give the measurements of
each separate plant, but have decided to do so, in order that it may be
seen that the superiority of the crossed plants over the
self-fertilised, does not commonly depend on the presence of two or
three extra fine plants on the one side, or of a few very poor plants on
the other side. Although several observers have insisted in general
terms on the offspring from intercrossed varieties being superior to
either parent-form, no precise measurements have been given (1/8. A
summary of these statements, with references, may be found in my
'Variation of Animals and Plants under Domestication' chapter 17 2nd
edition 1875 volume 2 page 109.); and I have met with no observations on
the effects of crossing and self-fertilising the individuals of the same
variety. Moreover, experiments of this kind require so much time--mine
having been continued during eleven years--that they are not likely soon
to be repeated.

As only a moderate number of crossed and self-fertilised plants were
measured, it was of great importance to me to learn how far the averages
were trustworthy. I therefore asked Mr. Galton, who has had much
experience in statistical researches, to examine some of my tables of
measurements, seven in number, namely, those of Ipomoea, Digitalis,
Reseda lutea, Viola, Limnanthes, Petunia, and Zea. I may premise that if
we took by chance a dozen or score of men belonging to two nations and
measured them, it would I presume be very rash to form any judgment from
such small numbers on their average heights. But the case is somewhat
different with my crossed and self-fertilised plants, as they were of