GROUP V. AXGIOSPERM.K : MONOCOTYLEDONES. 



477 



and the growing point 

 of the stem lateral, in 

 some forms the grow- 

 ing-point of the stem 

 is terminal (apical) on 

 the longitudinal axis of 

 the embryo (e.g. Dios- 

 coreacese). The grow- 

 ing-point of the prim- 

 ary stem frequently 

 developes into a plum- 

 ule. The axis of the 

 embryo terminates pos- 

 teriorly in a short 

 radicle. 



On germination, the 

 tipper end of the co- 

 tyledon commonly re- 

 mains in the seed and 

 absorbs the nutritious 

 substances deposited in 

 the endosperm (Fig. 

 291 II.-IV.} ; the lower 

 part of the cotyledon 

 elongates and pushes 

 the rest of the embryo 

 out of the seed. In 

 Grasses the cotyledon 

 has a peculiar shield- 

 like form, and is termed 

 the scutellum (Fig. 292 

 sc) : in the ripe seed it 

 almost entirely encloses 

 the embryo, and is in 

 contact by its outer 

 surface with the endo- 

 sperm ; during germin- 

 ation the cotyledon 

 absorbs the nutritious 

 matters contained in 

 the endosperm, while the stem with the other leaves grows out 



FIG. 291. Germination of PTweiiu dactylifera, the 

 Date. I. Transverse section of the dormant seed. II, III, 

 IV, Different stages of (Termination (IF. the natural 

 sire). A Transverse section of the seed at x x in IF. 

 B Transverse section of the seedling at x y : C at * i. 

 e The horny endosperm ; s the sheath of the cotyledon ; 

 *< ita stalk; cits apex developed into on organ of ab- 

 sorption which gradually consumes the endosperm and 

 at length occupies its place; w the primary root; w' 

 secondary roots ; b' I" the leaves which succeed the 

 cotyledon ; (b") becomes the first foliage-leaf, in B and C 

 its folded lamina is seen cut across. (After Sachs.) 



