-MoUi-ilOLOGY 



54 



of tlir plumule thai is, the leaves of the embrvo are alternate, 

 lint the eauliele is usually very short, ami there i> u,. external 



niark by which its limiN may l.e di>tin- 

 guUhed from the cotyledon, until gcrmi- 

 nation ha- begun. For a type of it. the 

 embryo of some aquatic or mar>h plants 

 may lie taken. \vh. iv it forms ihe whole 

 k'' 1 ' 1 "' 1 of the seed (Fig. 50-53), and 

 63 the structure can he made out antecedent 

 to germination. It is understood l.y supposing that the cotyle- 

 don, which forms its principal bulk (the caulicle being only the 

 very short thickish base), is convolute around a short 

 plumule, and the margins concreted, except a minute 

 longitudinal chink at base, out of which the growing 

 plumule protrudes in germination. The embryo of 

 his may he similar in structure, hut no distinction 

 of parts is visihle. It is very small in proportion to 

 the size of the seed, the kernel being mostly albu- 

 men, a supply of food, from which the germinating 

 embryo draws the materials of its growth. When 

 this takes place, either the cotyledon or the whole 

 embryo lengthens, its lower part is pushed out of the 

 seed, a root forms at the free end of the excessively 

 short caulicle. and the plumule develops from the 

 other in a series of one-leaved nodes, the internodes 

 of which remain so short that the leaves continue 

 in close contact, the bases of the older successhely 

 enclosing the inner and younger. (Fig. ,">5.) Here. 

 therefore, the cotyledon mainly remains in the seed, 

 and the seed remains underground ( hypog;eoiis) . 



40. It is somewhat dilferent in the Onion, which 

 has a similar embryo, except that it is longer, and 

 the cotyledon is curved in the albumen of the seed. 

 The iirsl steps are 1 he same as in Iris; but as soon 

 as a root is formed and embedded in the soil, the 

 cotyledon lengthens vastly more, into a long and 

 liliform green leaf, which, taking an erect position. 



I'll 1 r.n. S 1 ofTri.nlcirliiii |i.-ilnsliv; I lie rh.-ij.hr. Ir.'iilinj; In tin str. !!;,' clialaxa :it tlir 



Miiinnil. tiiru-'il tnwiirils I In <>< 51. Tl mlu-> ,> ilrt.-irlicd IVuni tbe Seed-COatS, ^Imwiiig 



the longitudinal chink at the base of the cotyledon; tlie short part below ia the radicle. 



\vi Hi tin' i-li ink timinl l:itcr:illy, and half the cotyledon CUl awny. IPI infill:,' to 



\i.'\\ Hi.' |iliniiuli' i-oiiccMli'd within. ''.'.. A rr,iss-srr| i,m through the plunml.-, inure 



ilicil. 

 ]'!! ;. .". I. Scclioii .if. -ci'il nf Iris. I'lil.ir.,'.'.!. >.li.i IIIL; tin- sin rill ninl .-iiiiciri-ntly siinplr 



c!iiiir\i> at the base of the albumen . r >.".. Ccnninatim: sr.'.i nn.l ser.liiir,' ,.i tin- s; ..f 



nntiinil si/c. 



