158 



one-fiftli of its composition, or varying in the 1,000 parts from 190 to 

 240. Separated by washing from the starch with which it is com- 

 bined in wheaten flour, this gluten is well known as an article of human 

 food in the forms of Macaroni, Vermacelli, &c., and may be classed 

 among the most nutritive of all vegetatable products ; containing, as it 

 does, from fourteen to sixteen per cent, of nitrogen, the element on 

 the presence of which vital action in animals seems mainly dependent. 

 The existence of only 109 parts of gluten in the thousand of rye, of 

 87 in the oat, and of 60 in barley, places all these grains in an infinitely 

 inferior grade to that of wheat of even the lowest cast in this respect. 

 In the chemical process of fermentation, gluten fulfils an important 

 function, hence the superior lightness of fine wheaten bread compared 

 with that made from barley and rye, &c. 



In agriculture and in commerce the varieties of wheat are often 

 distinguished as red and white wheats, and hard and soft wheats. Such 

 classification is altogether independent of value in a botanical point of 

 view, however important the latter division may be as regards the 

 economical adaptation of the particular kinds so denominated. Both 

 of these distictions are more or less results of soil, climate, and other 

 fortuitous circumstances, and are consequently liable to disturbance, or 

 even inversion, under a change of treatment, especially when subjected 

 to the same through several successive seasons. Colour, both in the 

 grain and chafi', is peculiarly Uable to change, red wheat becoming 

 white, and vice versa. The alteration of the texture of the grain, as 

 from hard to soft, is a longer process, requiring, in most cases, the 

 cultivation of several successive years ; but it will be found by experi- 

 ment no less certain than the change of colour — ^in fact, that none of 

 the popular distinctive characters of our cultivated wheats are absolutely 

 permanent, and therefore is it probable that they are, without excep- 

 tion, only so many forms of one original species. 



The varieties grown in this country, and almost throughout Northern 

 Europe, belong to the soft-grained class ; the hard-grained requiring a 

 warmer climate, or at least a higher mean summer temperature, are 

 almost exclusively raised in the eastern parts of the Continent and in 

 the countries around the basin of the Mediterranean. These latter 

 varieties are usually far richer in gluten than the soft wheats, containing 

 sometimes, it is stated, no less than thirty per cent, of that valuable 

 proximate, the proportion of which seems to be enhanced by the warmth 

 and dryness of the climate under which the grain is ripened. 



The variety figured on plate CXXVIII as Triticum compositum, is 

 seldom grown in England, unless as a subject of curiosity. It is sup- 

 posed to have originated among the ancient Egyptians, and to be the 

 one referred to in Pharaoh's dream as bearing seven ears on one stalk. 

 The number of its associated ears or branches is liable to considerable 

 variation ; and the ears are often simple on stalks, from the same root 

 that bears the compound ones, in which case they are indistinguishable 

 from those of T. Turgidum, another of the many pseudo-species 

 adopted by agricultural writers. 



Wheat is no less liable than rye, and, indeed, all kinds of corn and 

 other cultivated vegetables, to disorders associated with the development 



