Barley belongs to the genus Hordeum, of which there are numerous species and varieties. Linnaeus and the earlier botanists recognized six species of cultivated barleys, but modern botanists usually consider all cultivated barleys as belonging to one species to which the name H. sativum has been given. Körnicke regards H. spontaneum, a very long thin-grained two-rowed barley (see below) which grows in the East, as being the parent form; but E. S. Beaven inclines to the view that wild species of more than one form were originally used as food and subsequently cultivated. The last-named author has drawn up a scheme of classification for the varieties and races of cultivated barleys.

Fig. 1.Fig. 2.Fig. 3.Fig. 4.
Six-rowed
barleys.		 Fig. 1.—H. hexastichum.

a. Three spikelets in situ on the rachis, showing short internodes.

b. Spike. Median spikelets uppermost, and with lower awns removed.

c. Spike. Lateral spikelets uppermost, and with lower awns removed.

Fig. 2.—H. vulgare.

a. Three spikelets in situ on the rachis, showing long internodes.

b. Spike. Median spikelets uppermost.

c. Spike. Lateral spikelets uppermost.

Two-rowed
barleys.		 Fig. 3.—H. zeocriton.

a, d. Spikelets. Rachis edgewise, showing short internodes.

b. Var. zeocrithum (fan barley). Spike converging.

c. Var. erectum (Goldthorpe). Spike parallel.

Fig. 4.—H. distichum.

a, d. Spikelets. Rachis edgewise, showing long internodes.

b. Var. nutans (Chevallier).

c. Ouchak barley.

Figures 1-4 redrawn from a paper by E. S. Beaven in Journ. Fed. Inst. Brewing (1902), 8. 542.

In an ear of barley the primary axis or rachis is divided into internodes of which there may be any number up to forty. Each internode bears three single-flowered spikelets arranged alternately on either side of the rachis. In the six-rowed varieties the whole of these spikelets attain maturity, whilst in the two-rowed varieties only one on each side of the rachis, viz. the median, develops. British beer is brewed principally from the malt made from home-grown two-rowed barleys. Of late years, however, it has been found advantageous to employ a proportion of malt made from the thinner and more husky foreign barleys, mostly six-rowed varieties. The corns of two-rowed barleys are as a rule plumper than those of six-rowed barleys.

The most favourite barley for malting purposes grown in the United Kingdom is the narrow-eared two-rowed H. distichum, commonly known as Chevallier, from the name of the original cultivator, the Rev. John Chevallier. Of late years the quantity of barley of the so-called Goldthorpe type (H. zeocriton), used for malting, has increased. The paleae or outer coverings of the corns of this variety are somewhat “greasy” in appearance, and do not adhere so closely to the corn as in the Chevallier. The corns of Goldthorpe barley possess a small dimple or transverse furrow near the basal end. Further the basal bristle or rachilla (the prolongation of the axis or point from which the corn was originally developed) is invariably covered with long hairs, whilst in the case of Chevallier it has generally very short hairs. In the variety of Chevallier known as Archer, however, the rachilla has somewhat long hairs. Further the corns of Chevallier barley lie nearly vertical, that is almost parallel to the rachis, whereas in Goldthorpe they are spread out at a greater angle, hence the name fan or peacock barley given to that variety commonly known as sprat. It is believed by some brewers that Goldthorpe barleys never yield malt of so high a quality as do Chevallier barleys. On the other hand, when well matured, Goldthorpes work evenly and freely on the malting floors; and from an agricultural point of view they have the advantage of standing up better against unfavourable weather conditions on account of their stouter straws. Numerous fresh varieties of barley are continually being introduced as a result of artificial cross-fertilization, but cross-fertilization rarely if ever occurs naturally.

Hungarian two-rowed barleys are excellent as regards quality, and command a high price. The so-called Californian Chevallier and Chilean Chevallier contain a certain admixture of the six-rowed H. vulgare.

Of the imported thin barleys may be mentioned Brewing Californian, Brewing Chilean, Danubian and Smyrna (Yerli), all for the most part six-rowed varieties; also Ouchak, consisting principally of a two-rowed variety. For the manufacture of grain spirit a malt of high diastatic activity is required, and this is largely made from a very thin barley shipped from Odessa.

In the common six-rowed English barley or Scottish bere (H. vulgare), the two lateral rows of spikelets springing from one side of the rachis, either partially or entirely intersect and overlap the alternate lateral spikelets which spring from the opposite side of the rachis. This has given rise to the term “four-rowed barley.” Figs. 1-4 show some typical barleys in the ear.

The production of new varieties by cross-fertilization has of late years attained a degree of almost mathematical precision by the application of the law of inheritance first discovered by Gregor Mendel in 1865, and brought to light in 1901 independently by de Vries, Correns and Tschermak.