4 6 



THE WHEAT PLANT 



a 



c P 



" right-handed " plants being those in which the right margin of the first 

 green leaf-blade as seen from the front is folded over the left, " left- 

 handed " being applied to those in which the left margin covers the right. 

 In Figs. 37 and 38 the order and mode of rolling of the leaves of 



the primary axis of 

 ,// the plant and the 



first two or three 

 lateral branches is 

 indicated. In the 

 majority of right- 

 handed plants the 

 first green leaf of 

 all the lateral shoots 

 of the main stem is 

 inserted on the left 

 side of the secondary 

 axis which bears it, 

 the axis being 

 viewed from the en- 

 dosperm side of the 



FIG. 37. Diagrams of three types of leaf arrangement, A, B, SC utellum : in those 



and C, in young primary shoots, s, Scutellum ; c, coleoptile ; 1-1 i r 



}, first foliage leaf; p l , p z , prophylls of first and second which are 



lateral shoots; a, first foliage leaf of shoot in axil of leaf j; handed the first 

 b, first foliage leaf of shoot in axil of second leaf f . 



green leal arises on 

 the right side of its 

 branch. In a small 

 percentage of cases 

 s an alternate arrange- 

 ment of the first 

 leaves on the lateral 

 shoots occurs (Figs. 

 37 and 38) : other 

 abnormalities are 

 met with both in 

 the succession and 

 in the folding of the 

 leaves. 



Out of 500 seed- 

 lings of a pure line of T. vulgar e (Squarehead type), I found 276 with the 

 left margin folded over the right, and 224 " right-over-left " : in a pure 

 line of T. turgidum (Blue Cone) 256 were " left-over-right " and 244 

 " right-over-left " : in both these cases there is a preponderance of 

 " left-over-right " plants. 



FIG. 38. Diagram of the axes and leaf arrangements in young 

 plant. 5, Scutellum; c, coleoptile; i, primary axis; n, 

 first, 12, second lateral axis of i ; }, first, f second foliage 

 leaf of primary axis ; /,,, prophyll of axis 12 ; T '.T, first leaf of 

 axis 12 ; ,,,, , prophyll of first lateral axis of axis 12. 



