THE ROOTS 



37 



of the leaves of the axis at right angles, and are parallel to the plane in 

 which the three pairs of seminal rootlets are found. 



The second and succeeding axes or shoots develop their own inde- 

 pendent system of adventitious roots, which follow the same general 

 arrangement in pairs as that of the primary stem, except that at the base 

 of each bud or axis of the second and subsequent order, a single root first 

 appears. Moreover the roots on one axis are always arranged in a longi- 

 tudinal plane at right angles to that 

 which includes the roots on the axis 

 of the previous order. The longi- 

 tudinal plane through the roots of the 

 first lateral shoot at the tillering node 

 cuts the plane of the roots of the 



120, 



FIG. 22. Arrangement of the seminal 

 roots and the adventitious roots at . 

 the "tillering" node of a young . 

 plant, sc, Scutellum pair ; ep, epi- 

 blast pair ; co, coleoptile pair ; a, 

 one of the pair of roots at first node 

 of primary stem ; b, one of pair at 

 second node of primary stem ; 1 1 , 

 first branch of primary axis; iza, 

 one of pair of roots at first node of 

 second branch of primary axis. 



col 



SC 



FIG. 23. Diagram of the arrange- 

 ment of the roots, stem axes, and 

 leaves in the previous figure. 



primary axis at right angles ; the sixth seminal root, which springs from 

 a point just above the epiblast, is in this plane (, Fig. 22). 



The adventitious roots do not begin to appear until long after the 

 leaves of the first or second buds have come above ground. In crops 

 sown in October and November, particularly when the autumn is wet, 

 their production is usually delayed until the end of the following January, 

 at which date the first pair at the tillering node is often not more than 

 half an inch long : after this date they develop more rapidly. Generally 

 about the first or second week in March the first roots at the base of the 



