Hair-Grass, or Aira, L. a genus of perennial plants, comprising 24 species ; of which 14 are indigenous; and of these the following deserve notice:

1. The cespitnsa, or Turfy Hair-grass, which grows in moist meadows and woods; flowers from June to August. This plant is frequently found in tufts, and occasions irregularities in the surface of meadows. It produces an abundant quantity of leaves ; and being the roughest and coarest of all the grasses in pasture and meadow-grounds, cattle seldom touch them, unless impelled by hunger. It would, therefore, amply repay the trouble of eradicating it, and substituting better grasses : for this purpose, the land should be first drained, and then the tufts of this noxious weed pared up and burnt. Its ashes are said to alford an excellent eellent manure. - Cows, goats, and swine eat the turfy hair-grass, but it is refused by horses.

2. The flexuosa, Heath or Wav-ed Mountain Hair-grass, growing on heaths, in woods, and barren pastures ; and flowering from June to August.

3. The caryophyllea, or Silver Hair-grass, which is common in sandy pastures ; and flowers in the month of July.

Mr. Stillingfleet, in his excellent Tracts relating, to Natural History, recommends the culture of both these last species, as being particularly well adapted for sheep-walks : for he has observed them always to abound in those counties which are celebrated for delicious mutton.

4. The aquatica, or Water Hair-grass, is found generally on the edges of pools and standing waters ; it flowers in the months of June and July. - This plant is a wholesome food for cattle, and deserves to be more generally known ; as it contributes much to the sweetness of the Cottenham cheese, and to the fine flavour of Cambridge butter.