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
exactly the same age, were subjected from first to last to the same
conditions, and were descended from the same parents. When only from two
to six pairs of plants were measured, the results are manifestly of
little or no value, except in so far as they confirm and are confirmed
by experiments made on a larger scale with other species. I will now
give the report on the seven tables of measurements, which Mr. Galton
has had the great kindness to draw up for me.
["I have examined the measurements of the plants with care, and by many
statistical methods, to find out how far the means of the several sets
represent constant realities, such as would come out the same so long as
the general conditions of growth remained unaltered.
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