30.  Graminaceae.—­Zea mays.

This plant is monoecious, and was selected for trial on this account, no other such plant having been experimented on. (6/8.  Hildebrand remarks that this species seems at first sight adapted to be fertilised by pollen from the same plant, owing to the male flowers standing above the female flowers; but practically it must generally be fertilised by pollen from another plant, as the male flowers usually shed their pollen before the female flowers are mature:  ‘Monatsbericht der K. Akad.’  Berlin October 1872 page 743.) It is also anemophilous, or is fertilised by the wind; and of such plants only the common beet had been tried.  Some plants were raised in the greenhouse, and were crossed with pollen taken from a distinct plant; and a single plant, growing quite separately in a different part of the house, was allowed to fertilise itself spontaneously.  The seeds thus obtained were placed on damp sand, and as they germinated in pairs of equal age were planted on the opposite sides of four very large pots; nevertheless they were considerably crowded.  The pots were kept in the hothouse.  The plants were first measured to the tips of their leaves when only between 1 and 2 feet in height, as shown in Table 6/97.

Table 6/97.  Zea mays.

Heights of plants measured in inches.

Column 1:  Number (Name) of Pot.

Column 2:  Crossed Plants.

Column 3:  Self-fertilised Plants.

Pot 1 :  23 4/8 :  17 3/8. 
Pot 1 :  12 :  20 3/8. 
Pot 1 :  21 :  20.

Pot 2 :  22 :  20. 
Pot 2 :  19 1/8 :  18 3/8. 
Pot 2 :  21 4/8 :  18 5/8.

Pot 3 :  22 1/8 :  18 5/8. 
Pot 3 :  20 3/8 :  15 2/8. 
Pot 3 :  18 2/8 :  16 4/8. 
Pot 3 :  21 5/8 :  18. 
Pot 3 :  23 2/8 :  16 2/8.

Pot 4 :  21 :  18. 
Pot 4 :  22 1/8 :  12 6/8. 
Pot 4 :  23 :  15 4/8. 
Pot 4 :  12 :  18.

Total :  302.88 :  263.63.

The fifteen crossed plants here average 20.19, and the fifteen self-fertilised plants 17.57 inches in height; or as 100 to 87.  Mr. Galton made a graphical representation, in accordance with the method described in the introductory chapter, of the above measurements, and adds the words “very good” to the curves thus formed.

Shortly afterwards one of the crossed plants in Pot 1 died; another became much diseased and stunted; and the third never grew to its full height.  They seemed to have been all injured, probably by some larva gnawing their roots.  Therefore all the plants on both sides of this pot were rejected in the subsequent measurements.  When the plants were fully grown they were again measured to the tips of the highest leaves, and the eleven crossed plants now averaged 68.1, and the eleven self-fertilised plants 62.34 inches in height; or as 100 to 91.  In all four pots a crossed plant flowered before any one of the self-fertilised; but three of the plants did not flower at all.  Those that flowered were also measured to the summits of the male flowers:  the ten crossed plants averaged 66.51, and the nine self-fertilised plants 61.59 inches in height; or as 100 to 93.