Chapter 4

CRUCIFERAE, PAPAVERACEAE, RESEDACEAE, ETC.

Brassica oleracea, crossed and self-fertilised plants.
Great effect of a cross with a fresh stock on the weight of the offspring.
Iberis umbellata.
Papaver vagum.
Eschscholtzia californica, seedlings from a cross with a fresh stock not more vigorous, but more fertile than the
self-fertilised seedlings.
Reseda lutea and odorata, many individuals sterile with their own pollen.
Viola tricolor, wonderful effects of a cross.
Adonis aestivalis.
Delphinium consolida.
Viscaria oculata, crossed plants hardly taller, but more fertile than the self-fertilised.
Dianthus caryophyllus, crossed and self-fertilised plants compared for four generations.
Great effects of a cross with a fresh stock.
Uniform colour of the flowers on the self-fertilised plants.
Hibiscus africanus.

[6. CRUCIFERAE.--Brassica oleracea.

VAR. CATTELL'S EARLY BARNES CABBAGE.

The flowers of the common cabbage are adapted, as shown by H. Muller, for cross-fertilisation, and should this fail, for self-fertilisation. (4/1. 'Die Befruchtung' etc. page 139.) It is well known that the varieties are crossed so largely by insects, that it is impossible to raise pure kinds in the same garden, if more than one kind is in flower at the same time. Cabbages, in one respect, were not well fitted for my experiments, as, after they had formed heads, they were often difficult to measure. The flower-stems also differ much in height; and a poor plant will sometimes throw up a higher stem than that of a fine plant. In the later experiments, the fully-grown plants were cut down and weighed, and then the immense advantage from a cross became manifest.

A single plant of the above variety was covered with a net just before flowering, and was crossed with pollen from another plant of the same variety growing close by; and the seven capsules thus produced contained on an average 16.3 seeds, with a maximum of twenty in one capsule. Some flowers were artificially self-fertilised, but their capsules did not contain so many seeds as those from flowers spontaneously self-fertilised under the net, of which a considerable number were produced. Fourteen of these latter capsules contained on an average 4.1 seeds, with a maximum in one of ten seeds; so that the seeds in the crossed capsules were in number to those in the self-fertilised capsules as 100 to 25. The self-fertilised seeds, fifty-eight of which weighed 3.88 grains, were, however, a little finer than those from the crossed capsules, fifty-eight of which weighed 3.76 grains. When few seeds are produced, these seem often to be better nourished and to be heavier than when many are produced.

The two lots of seeds in an equal state of germination were planted, some on opposite sides of a single pot, and some in the open ground. The young crossed plants in the pot at first