[13]

Sept 11. 1878 Beet— seedlings Apogeotropism of Hypocotyl.

[14]

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Ipomoea

great-grandchildren. It thus appears that Hero and its descendants have varied in constitution so as to differ in an extraordinary manner from the ordinary plants of the present species.

Although the plants raised during the successive generations from crosses between distinct yet inter-related plants almost invariably exceeded in height, constitutional vigour, and fertility their self-fertilised opponents, it has been proved that seedlings raised by crossing two flowers on the same plant are by no means superior, on the contrary are somewhat inferior in height and weight to seedlings raised from flowers fertilised by with their own pollen. This is a remarkable fact, which seems to indicate that self-fertilisation is in some manner more advantageous than crossing, unless the cross brings with it, as is generally the case, some decided and preponderant advantage; but to this subject I shall recur in a future chapter.)

The advantages which is thus so generally gained by follow from a cross between two distinct plants apparently depends on the two plants differing somewhat in constitution or character.

This is shown by the seedlings from the intercrossed