588 



BOTANY 



PART II 



they lose some of their resistance to such dangers as extremes of temperature and 

 desiccation ; their former resistance was due to the small proportion of water they 

 contained. The next step is the rupture of the seed-coat, which, as a rule, is 

 effected by the emerging root. The root at once bends downwards geotropically 

 and, by means of its root-hairs, which are especially long and numerous at the 



FIG. 579. Seedlings, a, of Scorzonera 

 humilis ; b, of Iris pseudamrus. (After 

 KLEBS.) 



FIG. 580. Section through the upper part 

 of the fruit of Acrocomia sclerocarpa. S, 

 The hard shell ; P, the plug which is 

 pushed out of the shell by the ger- 

 minating embryo, K ; E, endosperm. 

 (After PFITZER.) 



FIG. 581. Kandelia Rheedii. The massive root of the 

 seedling (1) has broken out of the fruit. When 

 the plant separates from the fruit the root will 

 become inserted into the muddy soil. (From 

 SCHIMPER'S Plant-Geography.) 



junction of the root and hypocotyl, fastens the seedling in the soil. Meanwhile 

 the hypocotyl grows and gradually emerges from the seed -coat, while the 

 cotyledons as a rule remain for a time enclosed in the latter and absorb the 

 remainder of the reserve material (Figs. 577, 579). This process leads to the 

 hypocotyl becoming more and more strongly curved, and the tension resulting 

 from its further growth withdraws the cotyledons from the seed -coat. The 

 seedling then becomes erect, the leaves are expanded and can assimilate, and thus 

 its independent life commences. The number of cotyledons is usually 2, but 

 in some genera of Coniferae varies from 3-oo (Fig. 578). 



