Linaria vulgaris.

It has been mentioned in the introductory chapter that two large beds of this plant were raised by me many years ago from crossed and self-fertilised seeds, and that there was a conspicuous difference in height and general appearance between the two lots.  The trial was afterwards repeated with more care; but as this was one of the first plants experimented on, my usual method was not followed.  Seeds were taken from wild plants growing in this neighbourhood and sown in poor soil in my garden.  Five plants were covered with a net, the others being left exposed to the bees, which incessantly visit the flowers of this species, and which, according to H. Muller, are the exclusive fertilisers.  This excellent observer remarks that, as the stigma lies between the anthers and is mature at the same time with them, self-fertilisation is possible. (3/8.  ‘Die Befruchtung’ etc. page 279.) But so few seeds are produced by protected plants, that the pollen and stigma of the same flower seem to have little power of mutual interaction.  The exposed plants bore numerous capsules forming solid spikes.  Five of these capsules were examined and appeared to contain an equal number of seeds; and these being counted in one capsule, were found to be 166.  The five protected plants produced altogether only twenty-five capsules, of which five were much finer than all the others, and these contained an average of 23.6 seeds, with a maximum in one capsule of fifty-five.  So that the number of seeds in the capsules on the exposed plants to the average number in the finest capsules on the protected plants was as 100 to 14.

Some of the spontaneously self-fertilised seeds from under the net, and some seeds from the uncovered plants naturally fertilised and almost certainly intercrossed by the bees, were sown separately in two large pots of the same size; so that the two lots of seedlings were not subjected to any mutual competition.  Three of the crossed plants when in full flower were measured, but no care was taken to select the tallest plants; their heights were 7 4/8, 7 2/8, and 6 4/8 inches; averaging 7.08 in height.  The three tallest of all the self-fertilised plants were then carefully selected, and their heights were 6 3/8, 5 5/8, and 5 2/8, averaging 5.75 in height.  So that the naturally crossed plants were to the spontaneously self-fertilised plants in height, at least as much as 100 to 81.

Verbascum thapsus.

The flowers of this plant are frequented by various insects, chiefly by bees, for the sake of the pollen.  Hermann Muller, however, has shown (’Die Befruchtung’ etc. page 277) that V. nigrum secretes minute drops of nectar.  The arrangement of the reproductive organs, though not at all complex, favours cross-fertilisation; and even distinct species are often crossed, for a greater number of naturally produced hybrids have been observed in this genus than in almost any other. (3/9.  I have given a striking case of a large