424 



BOTANY. 



About this time there is inmost cases a slight differentiation 



of the inner cells, 



/r/&g:?\ /?^f^\ / ' foreshadowing the 



future tissue sys- 

 tems (///. a n d 

 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 disuil end 

 of the thallns-like 

 structure, and the 

 depression between 



Fig. 310,-Developmcnt of the embryo of Capsella them becomes the 

 Bwrxii-pastorii (highly magnified). /.. >. snspensor, or 

 pro-embryo of five cells, and terminated by a four-celled 

 embryo; 1-1, the longitudinal wall which divided the 

 first embryo-cell into two cells; 2-2. transverse wall 

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

 ing it four celled. //., v. snspensor; h, the hypophysis, 



fionis (V., Fig. 

 310). The root is 



the basal part of tl.e embryo" formed by th.- ilivi.ion of the last portion of 



1 of the snspensor ; the shaded portion of the 

 nbryo is the dcrmatog.-n or primary epidermis ///., the CinbryO fomi- 



il> 



embryo further advanced; the iui .-,,....... ^ c ..= ,..- , . . 



etitute the plerome, between these and the dermatogen CU I its Cap (the l)ll- 



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



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



older condition. V., embryo considerably advanced ; -j i 



c, c. cotyledons ; . apex of stem ; the dermatogen, perl- Cd tl'Om a layer OI 



Mem, and pb-rome shown as before; w, the rudiment- n .vn V00 nlrino- frnm 



ary root, and root-cap formed from the cell h' of HI. CCllS ICSUltlllg IlOm 



and /K-After Hiiwtein. t l )C succeg8 i ve fis- 



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



