170 



STRUCTURAL BOTANY 



-pi 



d- 



Fio. 68. Part of tran verse sec- 

 tion of root of a Liliaceous 

 plant, showing the first origin 

 of a rootlet, en, endoderrais ; 

 pe, pericycle ; x, xylem group ; 

 ph, phloem group ; co, con- 

 junctive tissue. All the above - 

 belong to the parent-root, s 

 (shaded), digestive sac, formed 

 from endodermis ; c, calyptro- 

 gen, or cells giving rise to the 

 root-cap of the rootlet ; p, peri- 

 blem, which will form its cortex 

 and piliferous layer ; pi, ple- 

 rome, from which the central 

 cylinder will be developed. 



Fic 70. Part of longitudinal 

 section of a monocotyledonous 

 root passing through a de- 

 veloping rootlet. Letters as 

 above. (All three Figs, are 

 magnified about 150, and are 

 after Van Tieghem and 

 Douliot.) 



ei'i. p'c. 



FIG 69. Similar section from the "White 

 Lily, showing a more advanced root- 

 let, d, cortex of parent-root, through 

 which the rootlet is boring its way ; 

 e, cortex at base of rootlet. Other 

 letters as above. 



layer of the root, which 

 bears the root-hairs, arises 

 here, however, from the 

 same group as the cortex, 

 instead of having a common 

 origin with the root-cap, as 

 in Dicotyledons (see Fig. 

 67, and compare it with 

 Fig. 33, p. 86). 



The branching of the root 

 can also be dismissed in a 

 few words, as in all im- 

 portant respects it takes 

 place in the same way as in 

 the Wallflower. 



