432 



FOURTH GROUP.— SEED-PLANTS. 



and other plants, but sometimes elongates and becomes marked out into distinct 

 internodes, as in Zea and other Gramineae. 



Fig. 336. Gerininalion of Phootix daclyli/era. I transverse, 

 section of the resting seed. //, ///, IV stages of germination (/K 

 tlie natural size). A transverse section of IV sx xx, B at .»y", C at zz. 

 e the horny endosperm, s sheath of the cotyledon, st its stalk, c its 

 summit developed as an organ of absorption which gradually exhausts 

 the endosperm and finally takes its place, tu the primary root, ?f'' secon- 

 dary roots, h root-cap,^' b" the leaves which come after the cotyledon. 

 b" becoming the first foliage-leaf. In B and C is a transverse section 

 of its folded lamina. 



Fig. 357. riant of PoIy^'Oiialiim mulli- 

 flotum in its second year. B its stem magnified. 

 The unbranched primary root is seen at 7v. lu 

 lateral roots springing from the stem st. t the 

 foliage-leaf of the second year, k its bud, c the 

 scar of insertion of the cotyledon, i and -z the 

 insertions of the two first sheath-leaves which 

 precede the foliage-leaf /. /, // the succeeding 

 sheath-leaves (scale-leaves) of the bud in B, 



The plant may increase in size and strength from such vigorous growth of the 

 axis of the embryo, that the latter ultimately becomes the primary stem of the full- 

 grown and fertile plant, as for instance in most Palms, Aloe, Zea, etc.; if the axis of 

 the embryo remains short while it strengthens, it may increase greatly in thickness and 

 form a tuber (P'ig. 359), or a bulb if the bases of the leaves become thicker, as 



