The perennial rye grass ([Fig. 109]) is very easily recognised by its flattened ears of alternate, stalkless spikelets. Each spikelet has only one glume. The leaves are dark-green and glossy, and the leaf-sheaths are flattened instead of being round, as is the case with most grasses. This is one of the most valuable of forage grasses.
Sweet-scented vernal grass ([Fig. 110]) does not occur very abundantly in meadows and pastures, but the fragrance of new-mown hay is almost wholly attributed to it. The odour can be distinctly perceived when a stalk of the grass is chewed. The leaves are somewhat hairy and are broad and flat. The spikelets are borne on short stalks. The flowers open early and are remarkable in possessing only two stamens instead of three.
Rushes and sedges are monocotyledonous plants which are often erroneously called grasses. The stems of rushes are vivid green, round, and pointed, and contain a distinct pith. The flowers ([Fig. 111]) are never in spikelets; they contain six stamens, and the pistil has three long stigmas. The sedges, like grasses, have narrow, pointed leaves, but the ligules are either very small or absent, and the leaf-sheaths are not split. The flowers are often in spikelets with glumes, as are grass flowers. The stems of sedges are solid and triangular.
Fig. 111.—A Rush. a, flowering part of stem;
single flower (b) and pistil (c) more highly magnified.
The flowers of rushes in many respects resemble those of the lily family. Indeed it is supposed that the ancestors, not only of the lily family, but also (along a different line) of the grasses and sedges, were primitive and now extinct rushes. The lilies have developed the rush perianth more and more as they have increasingly depended on insects for pollination; while in the grasses and sedges the perianth has gradually dwindled because these plants found that wind-pollination was sufficient for their needs.
EXERCISES ON CHAPTER VII.
1. What grasses are grown as corn in your part of the country? How can you recognise the grasses (a) before flowering, (b) in the ear, (c) by the straw?
2. What forage grasses are most cultivated in your part of the country? Make a list of the earliest dates on which you have seen each in flower.