Every one knows how greatly the various kinds of cabbage differ in appearance. In the Island of Jersey, from the effects of particular culture and of climate a stalk has grown to the height of sixteen feet, and "had its spring shoots at the top occupied by a magpie's nest:" the woody stems are not unfrequently from ten to twelve feet in height, and are there used as rafters (9/64. 'Cabbage Timber' 'Gardener's Chronicle' 1856 page 744, quoted from Hooker 'Journal of Botany.' A walking-stick made from a cabbage-stalk is exhibited in the Museum at Kew.) and as walking-sticks. We are thus reminded that in certain countries plants belonging to the generally herbaceous order of the Cruciferae are developed into trees. Every one can appreciate the difference between green or red cabbages with great single heads; Brussel-sprouts with numerous little heads; broccolis and cauliflowers with the greater number of their flowers in an aborted condition, incapable of producing seed, and borne in a dense corymb instead of an open panicle; savoys with their blistered and wrinkled leaves; and borecoles and kails, which come nearest to the wild parent-form. There are also various frizzled and laciniated kinds, some of such beautiful colours that Vilmorin in his Catalogue of 1851 enumerates ten varieties which are valued solely for ornament. Some kinds are less commonly known, such as the Portuguese Couve Tronchuda, with the ribs of its leaves greatly thickened; and the Kohlrabi or choux-raves, with their stems enlarged into great turnip-like masses above the ground; and the recently formed new race (9/65. 'Journal de la Soc. Imp. d'Horticulture' 1855 page 254 quoted from 'Gartenflora' April 1855.) of the choux-raves, already including nine sub- varieties, in which the enlarged part lies beneath the ground like a turnip.
Although we see such great differences in the shape, size, colour, arrangement, and manner of growth of the leaves and stem, and of the flower-stems in the broccoli and cauliflower, it is remarkable that the flowers themselves, the seed-pods and seeds, present extremely slight differences or none at all. (9/66. Godron 'De l'Espece' tome 2 page 52; Metzger 'Syst. Beschreibung der Kult. Kohlarten' 1833 s. 6.) I compared the flowers of all the principal kinds; those of the Couve Tronchuda are white and rather smaller than in common cabbages; those of the Portsmouth broccoli have narrower sepals, and smaller, less elongated petals; and in no other cabbage could any difference be detected. With respect to the seed-pods, in the purple Kohlrabi alone, do they differ, being a little longer and narrower than usual. I made a collection of the seeds of twenty- eight different kinds, and most of them were undistinguishable; when there was any difference it was excessively slight; thus, the seeds of various broccolis and cauliflowers, when seen in mass, are a little redder; those of the early green Ulm savoy are rather smaller; and those of the Breda kail slightly larger than usual, but not larger than the seeds of the wild cabbage from the coast of Wales. What a contrast in the amount of difference is presented if, on the one hand, we compare the leaves and stems of the various kinds of cabbage with their flowers, pods, and seeds, and on the other hand the corresponding parts in the varieties of maize and wheat! The explanation is obvious; the seeds alone are valued in our cereals, and their variations have been selected; whereas the seeds, seed- pods, and flowers, have been utterly neglected in the cabbage, whilst many useful variations in their leaves and stems have been noticed and preserved from an extremely remote period, for cabbages were cultivated by the old Celts. (9/67. Regnier 'De l'Economie Publique des Celtes' 1818 page 438.)
It would be useless to give a classified description (9/68. See the elder De Candolle in 'Transact. of Hort. Soc.' volume 5; and Metzger 'Kohlarten' etc.) of the numerous races, sub-races, and varieties of the cabbage; but it may be mentioned that Dr. Lindley has lately proposed (9/69. 'Gardener's Chronicle' 1859 page 992.) a system founded on the state of development of the terminal and lateral leaf-buds. Thus:
I. All the leaf-buds active and open, as in the wild-cabbage, kail, etc.
II. All the leaf-buds active, but forming heads, as in Brussel-sprouts, etc.
III. Terminal leaf-bud alone active, forming a head as in common cabbages, savoys, etc.
IV. Terminal leaf-bud alone active, and open, with most of the flowers abortive and succulent, as in the cauliflower and broccoli.
V. All the leaf-buds active and open, with most of the flowers abortive and succulent, as in the sprouting-broccoli. This latter variety is a new one, and bears the same relation to common broccoli, as Brussel-sprouts do to common cabbages; it suddenly appeared in a bed of common broccoli, and was found faithfully to transmit its newly-acquired and remarkable characters.
The principal kinds of cabbage existed at least as early as the sixteenth century (9/70. Alph. De Candolle 'Geograph. Bot.' pages 842 and 989.), so that numerous modifications of structure have been inherited for a long period. This fact is the more remarkable as great care must be taken to prevent the crossing of the different kinds. To give proof of this: I raised 233 seedlings from cabbages of different kinds, which had purposely been planted near each other, and of the seedlings no less than 155 were plainly deteriorated and mongrelised; nor were the remaining 78 all perfectly true. It may be doubted whether many permanent varieties have been formed by intentional or accidental crosses; for such crossed plants are found to be very inconstant. One kind, however, called "Cottager's Kail," has lately been produced by crossing common kail and Brussel- sprouts, recrossed with purple broccoli (9/71. 'Gardener's Chronicle' February 1858 page 128.), and is said to be true; but plants raised by me were not nearly so constant in character as any common kind of cabbage.
Although most of the kinds keep true if carefully preserved from crossing, yet the seed-beds must be yearly examined, and a few seedlings are generally found false; but even in this case the force of inheritance is shown, for, as Metzger has remarked (9/72. 'Kohlarten' s. 22.) when speaking of Brussel-sprouts, the variations generally keep to their "unter art," or main race. But in order that any kind may be truly propagated there must be no great change in the conditions of life; thus cabbages will not form heads in hot countries, and the same thing has been observed with an English variety grown during an extremely warm and damp autumn near Paris. (9/73. Godron 'De l'Espece' tome 2 page 52; Metzger 'Kohlarten' s. 22.) Extremely poor soil also affects the characters of certain varieties.