THE STEMS 



69 



leaf of the primary axis, -f* the 2nd leaf on the 2nd branch of the first 

 axis, and so on (Fig. 59). 



Very distinct differences in the habit of growth are visible in autumn 

 and early spring among young wheat plants of different varieties. Two 

 extreme types are readily recognised, namely, (i) the erect type (Fig. 65), 

 with shoots which spring up almost vertically, and (2) the prostrate type, 

 whose leafy shoots lie on the surface of the soil ; between these is (3) an 

 intermediate type (A and B, Fig. 66), with shoots which grow up at a variable 

 angle with the horizon. The three types may be indicated by the symbols 

 | , / , : these characters are constant and are easily distinguished 

 except when the plants are abnormally crowded and " tillering " is checked. 



A 



D 



FIG. 63. A, Diagram of the arrangement of the axes of a young plant ; li, relative 

 position of the axes later ; t, scutellum ; c, coleoptile ; /, first foliage leaf ; p,p', prophyll*. 



In those of erect habit the young shoots form a somewhat compact 

 tuft, and the culms of the mature plant converge at the base to a narrow 

 point just below ground, resembling the ribs of a nearly closed umbrella 

 (A, Fig. 67) : they are very liable to lodge and are easily pulled out of the 

 soil. The tendency to grow in this manner is sometimes seen in plants 

 with only two leaf-blades developed, the first blade then making but a 

 narrow angle with the second. 



In plants of the prostrate habit the first leaf-blade becomes horizontal 

 soon after the second blade appears. Later, the several shoots of the young 

 plant curve away from each other and soon come to lie close to the surface 



