The Roots of the IVheat Plant. 



173 



. a 



The corn or cereal grasses are cultivated for their seeds, which 

 consist of the following parts : — the perisperm (diagram 1 a), 

 which supports b, the embryo, 

 with its radicle, c, from which in 

 germination proceed the roots ; 

 and d, a plumule or bud, which 

 forms the ascending axis to 

 support the leaves, and ulti- 

 mately flowers and fruits or 

 seeds. These parts are in- 

 cluded in an integument of two 

 membranes (e), which, after 

 grinding, in wheat, is left as 

 the bran. 



e . 



h ,.-" 



,- ./ 



- c 



Diagram 1.— Grain of IVheat \. 



Now, in a perfectly well-formed grain of wheat, the exterior 

 will be plump and rounded, the integuments unbroken and not 

 shrivelled. But grain of all kinds is liable to be poor and thin, 

 and so capable of yielding but little feculent matter, a principle 

 upon which its feeding properties and commercial value mainly 

 depend. And it is also subject to many forms of disease, one of 

 which, ergot, results in a most exaggerated form of the grain, 

 and converts what would otherwise be nutritious constituents 

 into matter that is said to act as a virulent poison. 



Amongst all the cereals, wheat takes the highest rank, a posi- 

 tion to which it is entitled from the quantity and agreeable 

 nature of the nutritive seeds, as also from the strength of consti- 

 tution of the plant, being suited to almost every climate, and 

 cultivated in most degrees of latitude from the torrid to the 

 frigid zone. 



This general adaptability to different climatal circumstances 

 is not, as might at first be supposed, due to a long list of distinct 

 species, as it is doubtful whether all wiieats ought not to be com- 

 prehended under one specific form ; but its very liability to 

 change of form and habit, that is, its facility of making varieties 

 under different methods of cultivation, such as sowing in atitumn 

 or spriitg. Its distinctive ccmstitution, such as hard// and delicate, 

 derived from the difference in climate of its accustomed place of 

 growth, and, indeed, even the varied proportionals of the che- 

 mical constituents of different forms, are all so many changes, 

 induced by the action of external circumstances upon a species 

 of plant highly susceptil)le of such influences, with, at the same 

 time, a wonderful facility of j)reserving tlie identity of each form 

 where such conditions are constant. 



It was for some time considered that wheat belonged to the 

 genus triticum, perhaps from the form of its spike of flowers and 

 the peculiar flavour of its herbage : tliis latter fact, which be- 



