434 



BOTAl^Y. 



About tMs time there is in most cases a slight differentiation 



of the inner cells, 

 foreshadowing the 

 future tissue sys- 

 tems {III. and 

 IV., Fig. 310). A 

 little later the cot- 

 yledons (one or 

 two) appear ; in 

 the Monocotyle- 

 dons, in one side of 

 the thallus - like 

 structure a depres- 

 sion forms, which 

 becomes the punc- 

 tum vegetationis of 

 the embryo, and 

 marks the limits of 

 the stem and single 

 cotyledon ; in the 

 Decotyledons two 

 cotyledons grow 

 out symmetrically 

 from the distal end 

 of the thallus-like 

 structure, and the 

 depression between 



Pig. 310.— Development of the embryo of Oapsdla them beCOmeS the 



5ws'i-»astoris (highly maKiiifled). /.. t), Mispensor, or „„,„„i.,m t 



pro-embryo of five cells, and terminated bv a fonr-celled pUThClUnl V&g6tCt~ 



embryo; 1-1. the longitudinal wall which divided the ///ir/^e 



first embryo-cell into two cells; 3-3. transverse wall ^*t>/iAA 

 which divided each cell of the two-celled embryo, mak- 

 ing it four celled. IL, v. suspensor; A, thf hypophysis, 

 the basal part of the embryo formed by the division of 

 the end cell of the suspensor ; the shaded portion of the 



embryo is the dermatog«-n or primary epidermis ///., the CmbrVO form- 



embryo further advanced; the inner shaded cells con- . •' 



Btiiute the plerome, between these and the dermatogen eu : its Cap (the pil- 



to the right and left are the cells of the periblem ; the , . % . i , 



hypophysis is divided into two cells. A, h'. IV., still COrlllza) IS develop- 



older condition. F-, embryo considerably advanced ; j j» ^ i « 



c, c. cotyledons ; «, apex of stem ; the dermatogen, perl- eCl Irom a layer 01 



blera, and plerome shown as before ; w, the rudiment- „„n„ „„„„ii.- j* 



ary root, and root-cap formed from the cell h' of III. CCUS resulting IrOm 



and/F.-AfterHanstein. ^^^ SUCCeSsivG ■ fis- 



sion of the penultimate cell of the suspensor, the hypophy- 



{V; Fig. 



310). The root is 

 the last portion of 



