The straw differs in being more or less hollow, and in quality. The ears (9/27. Loiseleur-Deslongchamps 'Consid. sur les Cereales' page 11.) differ in colour and in shape, being quadrangular, compressed, or nearly cylindrical; and the florets differ in their approximation to each other, in their pubescence, and in being more or less elongated. The presence or absence of barbs is a conspicuous difference, and in certain Gramineae serves even as a generic character (9/28. See an excellent review in Hooker 'Journ. of Botany' volume 8 page 82 note.); although, as remarked by Godron (9/29. 'De l'Espece' tome 2 page 73.) the presence of barbs is variable in certain wild grasses, and especially in those such as Bromus secalinus and Lolium temulentum, which habitually grow mingled with our cereal crops, and which have thus unintentionally been exposed to culture. The grains differ in size, weight, and colour; in being more or less downy at one end, in being smooth or wrinkled, in being either nearly globular, oval, or elongated; and finally in internal texture, being tender or hard, or even almost horny, and in the proportion of gluten which they contain.
Nearly all the races or species of wheat vary, as Godron (9/30. Ibid tome 2 page 75.) has remarked, in an exactly parallel manner,--in the seed being downy or glabrous, and in colour,--and in the florets being barbed or not barbed, etc. Those who believe that all the kinds are descended from a single wild species may account for this parallel variation by the inheritance of a similar constitution, and a consequent tendency to vary in the same manner; and those who believe in the general theory of descent with modification may extend this view to the several species of wheat, if such ever existed in a state of nature.
Although few of the varieties of wheat present any conspicuous difference, their number is great. Dalbret cultivated during thirty years from 150 to 160 kinds, and excepting in the quality of the grain they all kept true; Colonel Le Couteur possessed upwards of 150, and Philippar 322 varieties. (9/31. For Dalbret and Philippar see Loiseleur-Deslongchamps 'Consid. sur les Cereales' pages 45, 70. Le Couteur on Wheat pages 6, 14-17.) As wheat is an annual, we thus see how strictly many trifling differences in character are inherited through many generations. Colonel Le Couteur insists strongly on this same fact. In his persevering and successful attempts to raise new varieties, he found that there was only one "secure mode to ensure the growth of pure sorts, namely, to grow them from single grains or from single ears, and to follow up the plan by afterwards sowing only the produce of the most productive so as to form a stock." But Major Hallett (9/32. See his Essay on 'Pedigree in Wheat' 1862; also paper read before the British Association 1869 and other publications.) has gone much farther, and by the continued selection of plants from the grains of the same ear, during successive generations, has made his 'Pedigree in Wheat' (and other cereals) now famous in many quarters of the world. The great amount of variability in the plants of the same variety is another interesting point, which would never have been detected except by an eye long practised to the work; thus Colonel Le Couteur relates (9/33. 'Varieties of Wheat' Introduction page 6. Marshall in his 'Rural Economy of Yorkshire' volume 2 page 9 remarks that "in every field of corn there is as much variety as in a herd of cattle.") that in a field of his own wheat, which he considered at least as pure as that of any of his neighbours, Professor La Gasca found twenty-three sorts; and Professor Henslow has observed similar facts. Besides such individual variations, forms sufficiently well marked to be valued and to become widely cultivated sometimes suddenly appear: thus Mr. Shirreff has had the good fortune to raise in his lifetime seven new varieties, which are now extensively grown in many parts of Britain. (9/34. 'Gardener's Chronicle' and 'Agricult. Gazette' 1862 page 963.)
As in the case of many other plants, some varieties, both old and new, are far more constant in character than others.