Barley (Hordeum sativum), a member of the grass family, and an important cereal which belongs peculiarly to temperate regions. It originated from a wild species, H. spontaneum, a native of western Asia and has been cultivated from the earliest times. Three subspecies or races are recognized, (i.) H. sativum, subsp. distichum (described by Linnaeus as a distinct species, H. distichon), two-rowed barley. Only the middle spikelet of each triplet is fertile; the ear has therefore only two longitudinal rows of grain, and the spikes are strongly compressed laterally. This approaches most nearly to the wild stock, from which it is distinguished by the non-jointed axis and somewhat shorter awns. This is the race most commonly grown in the British Isles and in central Europe, and includes a large number of sub-races and varieties among which are the finest malting-barleys. The chief sub-races are (a) peacock, fan or battledore barley, described by Linnaeus as a distinct species, H. zeocriton, with erect short ears about 2½ in. long, broad at the base and narrow at the tip, suggesting an open fan or peacock's tail; (b) erect-eared barleys (var. erectum) with erect broad ears and closely-packed plump grains; (c) nodding barleys (var. nutans). The ripe ears of the last hang so as to become almost parallel with the stem; they are narrower and longer than in (b), owing to the grains being placed farther apart on the rachis; it includes the Chevalier variety, one of the best for malting purposes, (ii.) H. sativum, subsp. hexastichum, six-rowed barley (the H. hexastichon of Linnaeus). All the flowers of each triplet of spikelets on both sides of the rachis are fertile and produce ripe fruits; hence the ear produces six longitudinal rows of grain.

The ears are short, erect, and the grain thin and coarse; the straw is also short. It is a hardy race, but owing to the poor quality of the grain is rarely met with in Great Britain, (iii.) H. sativum, subsp. vulgare, bere, bigg or four-rowed barley (the H. vulgare of Linnaeus). All the flowers of each triplet are fertile as in (ii.), but the rows are not arranged regularly at equal distances round the rachis. The central fruits of each triplet form two regular rows, but the lateral spikelets form not four straight single rows as in (ii.), but two regular double rows, the whole ear appearing irregularly four-rowed. This race seems to be of later origin than the others. The ears are erect, about 2½ in. long, the grains thinner and longer than in the two-rowed race, and the awns stiff and firmly adhering to the flowering glume. The var. pallidum is the barley most frequently cultivated in northern Europe and northern Asia. This race was formerly used for malt and beer, but owing to its larger amount of gluten as compared with starch it is less adapted for brewing than the two-rowed sorts.

To this belong the varieties naked barley (H. coeleste and H. nudum) and Himalayan barley (H. trifurcatum and H. aegiceras). In both the fruits fall out freely from the glume, and in the latter the awns are three-pronged and shorter than the grain.

Barley is the most hardy of all cereal grains, its limit of cultivation extending farther north than any other; and, at the same time, it can be profitably cultivated in sub-tropical countries. The opinion of Pliny, that it is the most ancient aliment of mankind, appears to be well-founded, for no less than three varieties have been found in the lake dwellings of Switzerland, in deposits belonging to the Stone Period. According to Professor Heer these varieties are the common two-rowed (H. distichum), the large six-rowed (H. hexastichum, var. densum), and the small six-rowed (H. hexastichum, var. sanctum). The last variety is both the most ancient and the most commonly found, and is the sacred barley of antiquity, ears of which are frequently represented plaited in the hair of the goddess Ceres, besides being figured on ancient coins. The cultivation of barley in ancient Egypt is indicated in Exod. ix. 31. Till within recent times barley formed an important source of food in northern countries, and barley cakes are still to some extent eaten.

Owing, however, to its poverty in that form of nitrogenous compound called gluten, so abundant in wheat, barley-flour cannot be baked into vesiculated bread; still it is a highly-nutritious substance, the salts it contains having a high proportion of phosphoric acid. The following is the composition of barley-meal according to Von Bibra, omitting the salts: -

Water

15

per cent.

Nitrogenous compounds

12.981

"

Gum

6.744

"

Sugar

3.200

"

Starch

59.950

"

Fat

2.170

"

Barley is now chiefly cultivated for malting (see Malt) to prepare spirits and beer (see Brewing), but it is also largely employed in domestic cookery. For the latter purpose the hard, somewhat flinty grains are preferable, and they are prepared by grinding off the outer cuticle which forms "pot barley." When the attrition is carried further, so that the grain is reduced to small round pellets, it is termed "pearl barley." Patent barley is either pot or pearl barley reduced to flour. Under the name decoctum hordei, a preparation of barley is included in the British Pharmacopoeia, which is of value as a demulcent and emollient drink in febrile and inflammatory disorders.