The Tall Fescue (_Festuca elatior_, fig. 21) is a larger and coarser form of _F. pratensis_, as seed of the latter will become the former by being sown on some stiff sandy clays. It occurs abundantly on the stiff alluvial deposits of our estuaries and river flats. It is an exceedingly coarse grass, with a tendency to grow in large separate bunches; and hence its presence is destructive to good pastures: it may, however, be encouraged as a rough growth in its indicated _habitats_. [Illustration: _Fig. 22._ Sheep’s Fescue.] Sheep’s Fescue (_Festuca ovina_, fig. 22) may be taken as the type of the small-leaved fescues. It is a native of our downs, and forms a large proportion of the sweet down sheep-pastures. It is known by its fine leaves, which come up immediately after the closest feeding; and if its quantity equalled its quality, it would be even more valuable than it is. A larger form, the Hard Fescue (_F. duriuscula_), is common to sound meadows and the hill valleys. This has much the same properties as the former, but it is taller, with longer and broader leaves. This should always be encouraged, and in laying down grass for permanent pasture, it should be plentifully added to the seed mixture. The Downy Wild Oat (_Avena pubescens_, fig. 23) is a common grass on thin calcareous soils. As it is very light in structure, and yields but little grass, it is not worth much as a first-rate pasture plant,—and indeed it would scarcely prefer to grow on them. There is, however, a smaller-flowered species, the _Avena flavescens_ (Yellow Oat-grass), which is better. It, too, occurs on chalky soils; while the _Avena pratensis_ (Meadow Oat-grass) is found too frequently in poor clays or on starved moors, in which its rigid leaves and harsh structure render it little, if any, better than a weed. [Illustration: _Fig. 23._ The Downy Wild Oat.] One of the most interesting species of the genus is the _Avena fatua_ (Wild Oat), well known as a weed in stiff arable soils. This is the parent of the crop oats in cultivation, and there is reason to know that by degeneracy the crop oat in some districts leaves behind a pest of wild oats.[2] [2] See “Natural History of British Meadow and Pasture Grasses,” by the Author. The Oat-like Grass (_Arrhenatherum avenaceum_, fig. 24), though a tall, succulent-looking species, is still too common in poor soils, as its herbage is bitter and nauseous, and not liked by cattle; and hay from it is always inferior in quality. It is sometimes recommended by seedsmen, and usually put with their mixtures; but we should at all times refuse it. [Illustration: _Fig. 24._ The Oat-like Grass.]