Fig. 85.—Dandelion. (× ¼.)
3. The thistle.—Compare the thistle ([Fig. 87]). The bracts are very prickly. Is this an advantage? Are the flowers tubular or strap-shaped? Examine the fruits (“thistle down”) and compare with those of dandelion.
The daisy.—What is generally called the “flower” of the daisy ([Fig. 84]) really consists of a very large number of small separate flowers set close together on a flattened disc or receptacle. The group of flowers is called a head. On the lower surface of the head are several green leaves, or bracts, which protect the bud before it opens. The flowers of a daisy-head are of two kinds. The white or pink straps set round the edge of the head are the corollas of the ray flowers. They have no stamens, but a pistil with a divided stigma is present in each. The disc flowers are yellow and tubular. The corolla consists of five united petals. On it are fixed five stamens, the anthers of which are joined together. The pistil is like that of a ray flower. No calyx is present in either the ray or disc flowers of the daisy.
The daisy is fertilised by the aid of insects which are attracted by the strap-like corollas of the ray flowers.
Fig. 86.—Dandelion. 1, two heads and a leaf (× ⅔);
2, a single flower (× 2); 3, fruit (× ⁸⁄₃);
4, receptacle, with one fruit.
The dandelion “flower” ([Fig. 85]) is also really a head consisting of a great many separate flowers. There are often between two and three hundred of these little flowers present in one head. Below the head are several green bracts, and these protect the flowers both in the bud and at night ([Fig. 86]). The flowers of the dandelion are all of one type. The corolla is strap-shaped ([Fig. 86], 2), and of a beautiful yellow colour to attract insects. On the end of the strap may be seen five small teeth which indicate that it really consists of five united petals. At the base of the corolla is a tuft of fine hairs, which is the top of the calyx-tube, and at the bottom of the flower is a little white knob—the ovary. The five stamens are fixed on the inside of the corolla-tube. Their anthers are united to form a tube through which the upper part of the style, and the forked stigma protrude.
