IRREGULAR METAMORPHOSIS OF PLANTS. 
107 
oblong, or fusiform; the epidermis from white to yellow, purple, and 
green. The celery, the root of which is fibrous when wild, produces, 
under domestication, a fleshy round root like a turnip, known in gar¬ 
dens by the name of celeriac. The common potato, the colour of 
which is usually yellow, produces a variety deeply stained, not on the 
skin only, but through its whole substance, with purple. The parsnep 
varies from fusiform to spherical; and there are hundreds of instances 
of the same kind, of which everybody must be aware. 
Metamorphosis of the stem is much less frequent than that of the 
root. The stems of the common cabbage are naturallv hard and 
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stringy ; but in a variety, called by the French, Chou moellier, the stem 
is succulent and fusiform ; and in the Kohl Rabi it forms a succulent 
tumour above the ground, in form and size resembling a turnip. In 
alpine situations the stem becomes shortened in proportion to the 
elevation at which it is produced, but it lengthens in low humid situa¬ 
tions. Domestication has rendered tall stems more dwarf, and dwarf 
stems taller; the common dahlia, the mean height of which may be 
estimated at six feet, has been reduced by cultivation to a stature not 
exceeding three. Cabbage and many other culinary plants have 
undergone a similar change; wdiile the common hemp has sported into 
a gigantic variety twice the usual size. The stems occasionally be¬ 
come bundled, that is, take the appearance of a number of separate 
stems connected together, side by side, as in the common cock’s-comb, 
Celosia. This was formerly believed to arise from the union of several 
stems ; a manifest error, as an inspection of a dissected stem will prove ; 
it is an extremely irregular formation, somewhat analogous to that 
which constantly obtains in Bauhinia. 
The leaves undergo a thousand metamorphoses, of which a few only 
need be noticed. They become succulent and turn inwards, forming 
what gardeners call a heart, as in the cabbage and lettuce. Their 
parenchyma extends more rapidly than the veins and margins; this 
produces puckering, .as in curled leaves. If the parenchyma and mar¬ 
gin are together produced in excess, we then have what gardeners call 
a curl, as in the plants known by the respective names of curled 
greens, curled cress, curled endive, &c. If this tendency to parenchy¬ 
matous dovelopment proceed much further, the surface is not merely 
puckered, but processes arise from it like small leaves. Scotch kale is 
an instance of this. Occasionally in compound leaves an unusual 
number of leaflets is produced, as seven instead of three ; a double 
pinnate leaf in some roses in lieu of a simple pinnate one. In other 
plants the reverse occurs; there is a dahlia which constantly produces 
simple leaves in room of compound ones. 
