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.  The principal methods that were adopted are easily explained by selecting one of the shorter series of plants, say of Zea mays, for an example.”

Table 1/1.  Zea mays (young plants). (Mr. Galton.)

Heights of Plants in inches: 

Column 1:  Number (Name) of Pot.

Column 2:  Crossed, as recorded by Mr. Darwin.

Column 3:  Self-fertilised, as recorded by Mr. Darwin.

Column 4:  Crossed, in Separate Pots, arranged in order of magnitude.

Column 5:  Self-fertilised, in Separate Pots, arranged in order of magnitude.

Column 6:  Crossed, in a Single Series, arranged in order of magnitude.

Column 7:  Self-fertilised, in a Single Series, arranged in order of magnitude.

Column 8:  Difference, in a Single Series, arranged in order of magnitude.

Pot 1 :  23 4/8 :  17 3/8 ::  23 4/8 :  20 3/8 ::  23 4/8 :  20 3/8 :  -3 1/8. 
Pot 1 :  12 :  20 3/8 ::  21 :  20 ::  23 2/8 :  20 :  -3 2/8. 
Pot 1 :  21 :  20 ::  12 :  17 3/8 ::  23 :  20 :  -3. 
Pot 1 :  — :  — ::  — :  — ::  22 1/8 :  18 5/8 :  -3 4/8. 
Pot 1 :  22 :  20 ::  22 :  20 ::  22 1/8 :  18 5/8 :  -3 4/8.

Pot 2 :  19 1/8 :  18 3/8 ::  21 4/8 :  18 5/8 ::  22 :  18 3/8 :  -3 5/8. 
Pot 2 :  21 4/8 :  18 5/8 ::  19 1/8 :  18 3/8 ::  21 5/8 :  18 :  -3 5/8. 
Pot 2 :  — :  — ::  — :  — ::  21 4/8 :  18 :  -3 4/8. 
Pot 2 :  22 1/8 :  18 5/8 ::  23 2/8 :  18 5/8 ::  21 :  18 :  -3. 
Pot 2 :  20 3/8 :  15 2/8 ::  22 1/8 :  18 ::  21 :  17 3/8 :  -3 5/8.