Watch insects visiting the flowers and try to make out how the pollination of the stigmas is brought about.
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 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.