We see this in our radishes, beet, and in the less generally known "turnip-rooted" celery, and in the finocchio, or Italian variety of the common fennel. Mr. Buckman has lately proved by his interesting experiments bow quickly the roots of the wild parsnip can be enlarged, as Vilmorin formerly proved in the case of the carrot. (9/79. These experiments by Vilmorin have been quoted by many writers. An eminent botanist, Prof. Decaisne, has lately expressed doubts on the subject from his own negative results, but these cannot be valued equally with positive results. On the other hand, M. Carriere has lately stated ('Gardener's Chronicle' 1865 page 1154), that he took seed from a wild carrot, growing far from any cultivated land, and even in the first generation the roots of his seedlings differed in being spindle-shaped, longer, softer, and less fibrous than those of the wild plant. From these seedlings he raised several distinct varieties.)
This latter plant, in its cultivated state, differs in scarcely any character from the wild English carrot, except in general luxuriance and in the size and quality of its roots; but ten varieties, differing in the colour, shape, and quality of the root, are cultivated in England and come true by seed. (9/80. Loudon's 'Encyclop. of Gardening' page 835.) Hence with the carrot, as in so many other cases, for instance with the numerous varieties and sub-varieties of the radish, that part of the plant which is valued by man, falsely appears alone to have varied. The truth is that variations in this part alone have been selected; and the seedlings inheriting a tendency to vary in the same way, analogous modifications have been again and again selected, until at last a great amount of change has been effected.
With respect to the radish, M. Carriere, by sowing the seed of the wild Raphanus raphanistrum in rich soil, and by continued selection during several generations, raised many varieties, closely like the cultivated radish (R. sativus) in their roots, as well as the wonderful Chinese variety, R. caudatus: (see 'Journal d'Agriculture pratique' tome 1 1869 page 159; also a separate essay 'Origine des Plantes Domestiques' 1869.) Raphanus raphanistrum and sativus have often been ranked as distinct species, and owing to differences in their fruit even as distinct genera; but Professor Hoffman ('Bot. Zeitung' 1872 page 482) has now shown that these differences, remarkable as they are, graduate away, the fruit of R. caudatus being intermediate. By cultivating R. raphanistrum during several generations (ibid 1873 page 9), Professor Hoffman also obtained plants bearing fruits like those of R. sativus.
PEA (Pisum sativum).
Most botanists look at the garden-pea as specifically distinct from the field-pea (P. arvense). The latter exists in a wild state in Southern Europe; but the aboriginal parent of the garden-pea has been found by one collector alone, as he states, in the Crimea. (9/81. Alph. De Candolle 'Geograph. Bot.' 960. Mr. Bentham 'Hort. Journal' volume 9 1855 page 141 believes that garden and field peas belong to the same species, and in this respect he differs from Dr. Targioni.) Andrew Knight crossed, as I am informed by the Rev. A. Fitch, the field-pea with a well-known garden variety, the Prussian pea, and the cross seems to have been perfectly fertile. Dr. Alefield has recently studied (9/82. 'Botanische Zeitung' 1860 s. 204.) the genus with care, and, after having cultivated about fifty varieties, concludes that certainly they all belong to the same species. It is an interesting fact already alluded to, that, according to O. Heer (9/83. 'Die Pflanzen der Pfahlbauten' 1866 s. 23.) the peas found in the lake-habitations of Switzerland of the Stone and Bronze ages, belong to an extinct variety, with exceedingly small seeds, allied to P. arvense or the field-pea. The varieties of the common garden-pea are numerous, and differ considerably from one another. For comparison I planted at the same time forty-one, English and French varieties.