Fig. 62.—A, Fruits of Shepherd’s Purse (× ½);Fig. 63.—Root of Fig. 64.—Root
B, a single open fruit (mag.); C, cross section of B. Turnip. (× ⅓.)of Radish. (× ½.)
Useful crucifers.—The turnip and the radish are largely cultivated for their roots ([Figs. 63 and 64]), and are then taken out of the ground at the end of their first season. As these plants naturally flower in their second year of growth and then die, they are called biennials. The production of flowers and fruit is a great strain on a plant, and it is to prepare for the effort that the turnip and radish store so much food in their roots during the first year as to give them a globular and spindle shape respectively. A carrot is not a crucifer, but it also adopts this device.
The cabbage is grown for its leaves. Varieties of the cabbage are Brussels sprouts, broccoli, and cauliflower; it is the very small flower-buds of the last two which are eaten. Cress and white mustard are eaten in the seedling stage. The seeds of the black mustard are ground and eaten as a condiment.
17. THE BUTTERCUP FAMILY.
1. The buttercup.—Notice the habit of growth, characters of the leaves, etc. Is the buttercup a dicotyledon? Make this observation with all flowering plants. (See, however, [Chap. VIII., p. 163].)
In the flowers of a buttercup ([Fig. 65]) make out:
(a) The calyx of five green, separate sepals; they are the only parts to be seen in young, unopened buds. Take off the sepals of a fully-opened flower one by one.
(b) The corolla of five, golden-yellow, separate petals, alternate with the sepals. Notice the nectary—a little pocket—near the base of the upper surface of each petal. Take off the petals one by one and observe that they are fixed on the receptacle, a little higher than the sepals.
(c) The large number of separate stamens, inserted still higher on the receptacle.
(d) On the top of the receptacle the large number of separate, flask-shaped bodies, which together make up the pistil. Each of these is called a carpel.