VIII.
DIFFERENCE BETWEEN CROSSED AND SELF-FERTILISED PLANTS IN CONSTITUTIONAL VIGOUR AND IN OTHER RESPECTS.
Greater constitutional vigour of crossed plants.—The effects of great crowding.—Competition with other kinds of plants.—Self-fertilised plants more liable to premature death.—Crossed plants generally flower before the self-fertilised.—Negative effects of intercrossing flowers on the same plant.—Cases described.—Transmission of the good effects of a cross to later generations.—Effects of crossing plants of closely related parentage.—Uniform colour of the flowers on plants self-fertilised during several generations and cultivated under similar conditions.