4 8 



THE WHEAT PLANT 



The narrow side is also slightly longer than the wider half, an arrangement 

 which places the attached auricles one below the other alternately. 



The blade of the first green leaf of the wheat plant differs from all the 

 succeeding ones in having a somewhat stiffened bluntish apex, in outline 

 like an arch, a form which enables the top to push its way through the 

 soil without damage (Figs. 35, 41). The characteristic and easily recog- 

 nised shape of this leaf greatly assists in the determination of the number 

 of separate plants in a crowded row of seedlings in the field. 



The blades of all other foliage leaves are drawn out into long acuminate 

 points which are slightly hooded. About i| to 2 inches from the top of a 

 full-grown leaf is a peculiar constriction, the margins curving inwards at 



that point giving to the blade the 

 appearance of being formed of two 

 pieces (3, Fig. 41). 



On the upper surface is a series 

 of longitudinal and slightly raised 

 ribs, which on the young leaves of 

 T. dicoccoides, T. dicoccum, and T. 

 turgidum are covered with soft 

 velvety hairs of nearly uniform 

 length ; in T. monococcum the hairs 

 are short and scabrid, in T. 

 durum the blades are glabrous, 

 while in T. vulgar e, T. Spelta, T. 

 aegilopoides there are long hairs on 

 the summits and shorter ones on the 

 FIG. 4 i. i, Apex of the first flanks of the ridges (Figs, in, i64). x 



foliage leaf; 2, apex of , u f T / ^ "Jj 



second foliage leaf; 3, apex I he long hairs ol 1. aegUopoides 

 of older leaf -blade (nat. ten d to disappear when the plants 



are brought under cultivation. 



The lower surface of the leaf is not ribbed and is usually smoother than 

 the upper surface. 



At the base of the upper surface of the leaf-blade is the ligule, a thin 

 membranous structure which closely invests the stem and prevents the 

 access of rain, dust, aphides, and other insects between the leaf-sheath 

 and the stem (/, Fig. 42). It is colourless, and its free edge is irregularly 

 cut and fringed with minute hairs. The ligules of the upper leaves are 

 from 3 to 4 mm. long, those of the lower leaves much shorter. 



The auricles are curved claw-like appendages attached to the base of 

 each leaf-blade, where they loosely clasp the sheath and stem from opposite 



1 The ridges and hairs on the surface of the leaf are readily seen on bending the blade 

 outwards and examining with a pocket lens ( x 8) the folded part as a silhouette against 

 the sky or other light background. 



FIG. 40. 

 Young leaf- 

 blade show- 

 ing spiral 

 twist (nat. 

 size). 



