ich vegetation in turn may prepare and
store up, in the course of a few weeks or months, the largest quantity
of solid nourishing material, in a form most available for food. Taking
advantage of this, man has transported the Potato from the cool Andes of
Chili to other cool climates, and makes it yield him a copious supply of
food, especially important in countries where the season is too short,
or the summer's heat too little, for profitably cultivating the
principal grain-plants.

[Illustration: Fig. 101. Tubers of Helianthus tuberosus, called
"artichokes."]

[Illustration: Fig. 102. Bulblet-like tubers, such as are occasionally
formed on the stem of a Potato-plant above ground.]

111. =The Corm or Solid Bulb=, like that of Cyclamen (Fig. 103), and of
Indian Turnip (Fig. 104), is a very short and thick fleshy subterranean
stem, often broader than high. It sends off roots from its lower end, or
rather face, leaves and stalks from its upper. The corm of Cyclamen goes
on to enlarge and to produce a succession of flowers and leaves year
after year. That of Indian Turnip is formed one year and is consumed
the next. Fig. 104 represents it in early summer, having below the corm
of last year, from which the roots have fallen. It is partly consumed by
the growth of the stem for the season, and the corm of the year is
forming at base of the stem above the line of roots.

[Illustration: Fig. 103. Corm of Cyclamen, much reduced in size: roots
from lower face, leaf-stalks and flower-stalks from the upper.]

[Illustration: Fig. 104. Corm of Indian Turnip (Arisaema).]

112. The corm of Crocus (Fig. 105, 106), like that of its relative
Gladiolus, is also reproduced annually, the new ones forming upon the
summit and sides of the old. Such a corm is like a tuber in budding from
the sides, i. e. from the axils of leaves; but these leaves, instead of
being small scales, are the sheathing bases of foliage-leaves which
covered the surface. It resembles a true bulb in having these sheaths or
broad scales; but in the corm or solid bulb, this solid part or stem
makes up the principal bulk.

[Illustration: Fig. 105. Corm of a Crocus, the investing sheaths or dead
leaf-bases stripped off. The faint cross-lines represent the scars,
where the leaves were attached, i. e. the nodes: the spaces between are
the internodes. The exhausted corm of the previous year is underneath;
forming ones for next year on the summit and sides.]

[Illustrati