The foxglove family.—In the primrose and the disc-flowers of the daisy are seen examples of regular, dicotyledonous flowers with five petals fused to form a corolla tube, and with five stamens inserted on the corolla. In the strap-shaped flowers of the dandelion the corolla is irregular, but still consists of five fused petals and bears the five stamens. Fig. 89.—Foxglove, (× ⅙.) The foxglove (Fig. 89) and its relatives have also irregular corollas of joined petals on which the stamens are fixed; but the stamens are usually only four in number, two being long and two short [Pg 116] as in Fig. 90, b. In the foxglove the stamens ripen and shed their pollen before the pistil of the same flower is mature. This prevents self-fertilisation, but bumble bees in passing from one flower to another convey the ripe pollen of the younger flowers to the stigmas of flowers which are ready for fertilisation. Fig. 90.—Foxglove. a, flower; b, corolla cut open and spread out; c, calyx and pistil; d, fruit; e, section of fruit. (× ⅔.) The pretty blue speedwell (Fig. 91) is closely related to the foxglove, but its corolla has only four lobes instead of five, and some times these seem of almost equal size at the first glance. Generally, however, the corolla is very plainly irregular. The speedwell has only two stamens, while mullein has five. Fig. 91.—Speedwell. (× ½.) Calceolaria, musk, gloxinia, and snapdragon—other members of the family—are often cultivated in gardens. The flowers of the musk are especially interesting, because they show so well what is called irritability,—the power which all living things possess of acting in a definite manner in response to a definite [Pg 117] irritation or stimulus. We have already seen good examples of plant-irritability in the way a climbing stem winds itself round a support. The stigma of the musk flower has two flaps. If these are touched with a hair or bristle they quickly close together, but presently open again as if they had found out that they had been tricked. When, however, a little pollen is put on the flaps they close finally, for their whole object is accomplished. Some of the plants in this family are poisonous, the foxglove being especially so in all its parts. 24. THE LABIATES. 1. The deadnettle.—Examine a deadnettle plant (Fig. 92). Notice the habit of growth, and write down a description of the shape and appearance of the stem and leaves. What is the shape of the flower? How many sepals, petals, and stamens has it? Do the stamens ripen first, or does the pistil? What insects do you find visiting the flower? Try to find out how they pollinate the stigma. Fig. 92.—White Deadnettle. (× ⅙.) 2. Other labiates.—Compare the sage (especially in respect of its relation to bees), rosemary, thyme, marjoram, and mint, and distinguish between their various flowers, leaves, and scents.