354 



CHENOPODIACE^ 



its exit (3, Fig. 109). Eventually the cotyledons become free from 

 the seed and appear above ground. The young plant possesses 

 two narrow cotyledons, a well-marked hypocotyl, and a primary 

 root, which is quite distinct from the latter (4, Fig. no). 



Roots and Hypocotyl. — The primary root is well-developed, 

 and secondary roots arise upon it in two longitudinal rows 

 (6, Fig. no). The total root-system is very extensive and often 

 penetrates to great depths in suitable 

 soil. It is not infrequent to find drains 

 4 and 5 feet below the surface of the soil 

 blocked by them. In the subsequent 

 growth of the plant the hypocotyl be- 

 comes pulled more or less into the ground 

 by the contraction of the roots, but the 

 hypocotyl and root always remain more 

 or less distinct ; the former rarely bears 

 any adventitious roots. 



The 'mangel' of the farm, which is 

 generally termed a 'root,' consists of 

 thickened hypocotyl and true root; the 

 relative proportion of each part is not 

 however, the same in all varieties. In 

 the long-red and ox-horn varieties the 

 hypocotyl grows out of the ground; in 

 others, such as the sugar-beet, the hypo- 

 cotyl is shorter and pulled beneath the 

 surface of the soil. 



A collection of leaves is seen at the 

 apex of the mangel, and just below them Jjf: "Xi^^t^uTtoi^t 

 are the remains of the old leaf-bases, "here cotyledon was 'present, 

 which give to this part a rough rugged appearance (Fig. 114). 



A transverse section (Fig. 112) shows a series of concentric 

 rings of firm vascular tissue alternating with rings of soft thin- 

 walled parenchymatous bast; the cell-sap of the parenchyma, 



