the Week of Proper 3 / Ordinary 8
1911 Encyclopedia Britannica
The violets comprise a large botanical genus (Viola) - in which more than 200 species have been described - found principally in temperate or mountain regions of the northern hemisphere; they also occur in mountainous districts of South America and South and Tropical Africa, while a few are found in Australasia. The species are mostly low-growing herbs with alternate leaves provided with large leafy stipules (fig. r). The flowers, which are solitary, or rarely in pairs, at the end of slender axillary flower-stalks, are very irregular in form, with five sepals prolonged at the base, and five petals, the lowest one larger than the others and with a spur, in which collects the honey secreted by the spurs of the two adjoining stamens. The five anthers are remarkable for the coloured processes which extend beyond the anther cells and form a sort of cone around the style (fig. 2). The ovary is superior and one-celled, with three parietal placentas and numerous ovules; it bears a single style, which ends in a dilated or hood-like stigma (fig. 3). The fruit is a capsule bursting loculicidally, i.e. through the centre of each of the three valves. By the contraction of the valves the small smooth seeds, which form FIG. 2. - Two Stamens of Viola tricolor (Pansy), with their two anther lobes and the processp extending beyond them. One of the stamens has been deprived of its spur; the other shows its spur, c. a row down the centre, are shot out to some little distance from she parent plant. The irregular construction of the flower is connected with fertilization by insect agency. To reach the honey in the spur of the flower, the insect must thrust its proboscis into the flower close under the globular head of the stigma. This lies in the anterior part of a groove fringed with hairs on the inferior petal. The anthers shed their pollen into this groove, either of themselves or when the pistil is shaken by the insertion of the bee's proboscis. The proboscis, passing down this groove to the spur, becomes dusted with pollen; as it is drawn back, it presses up the lip-like valve of the stigma so that no pollen can enter the stigmatic chamber; but as it enters the next flower it leaves some pollen on the upper surface of the valve, and thus cross-fertilization is effected. In the sweet violet, V. odorata and other species, inconspicuous permanently closed or "cleistogamic" flowers (fig. 4) occur of a FIG. 3. - Pistil of Viola tricolor (Pansy). 1. Vertical section to show the ovules o, attached to the parietes. Two rows of ovules are seen, one in front and the other in profile. p, a thickened line on the walls forming the placenta; c, calyx; d, ovary; s, hooded stigma terminating the short style. 2. Horizontal section of the same. p, placenta; o, ovules; s, suture, or median line of carpel.
greenish colour, so that they offer no attractions to insect visitors and their form is correspondingly regular. The anthers are so situated that the pollen on escaping comes into contact with the stigma; in such flowers self-fertilization is compulsory and very effectual, as seeds in profusion are produced.