6 ROOT 



apex than the last-formed lateral roots ; so that the youngest 

 and smallest of fhem are seen to be nearest to the tip of 

 the main root (fig. 4). T/ie lateral roots are therefore said 

 to arise in acropetal succession. They do not appear at 

 indifferent points; on the contrary, they emerge only on 

 certain determined sides of the main root, so as to form 

 regular ranks or rows along the length of the latter. For 



Fig. 4. — Development of a typical Dicotyledon. 



example, the branches of a Wallflower-root form two rows, 

 while those of the Creeping Buttercup-root are ranged in 

 four rows.* 



Adventitious Boots. — Lateral roots frequently arise on stems 

 — for instance, on the creeping stems of the Strawberry 

 (fig. 54), Creeping Buttercup, and Grasses; or on the under- 

 ground parts of the stem of the Primrose or on " Cuttings." 

 Inasmuch as these roots do not arise in the normal method — 



* One important character concerning the origin of lateral roots is that 

 they arise as internal growths, which push their way through the rind of 

 the mother-root, and eventually reach the soil. They are said to be 

 endogenous (arising within) in origin. 



