the wild English species, except in general luxuriance and in the size
and quality of its roots; but in the root ten varieties, differing in
colour, shape, and quality, are cultivated[595] in England, and come
true by seed. 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.

_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.[596] 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. Alefeld
has recently studied[597] the genus with care, and, after having
cultivated about fifty varieties, concludes that they all certainly
belong to the same species. It is an interesting fact already alluded
to, that, according to O. Heer,[598] 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 field-pea. The varieties of the common garden-pea are
numerous, and differ considerably from each other. For comparison I
planted at the same time forty-one English and French varieties, and in
this one case I will describe minutely their differences. The varieties
{327} differ greatly in height,--namely from between 6 and 12 inches to
8 feet,[599]--in manner of growth, and in period of maturity. Some
varieties differ in general aspect even while only two or three inches
in height. The stems of the _Prussian_ pea are much branched. The tall
kinds have larger leaves than the dwarf kinds, but not in strict
proportion to their height:--_Hairs' Dwarf Monmouth_ has very large
leaves, and the _Pois nain hatif_, and the moderately tall _Blue