HISTOLOGY OF ANGIOSPERM STEM, ROOT, ETC. 131 



in the embryo-sac note the embryo, which is attached to 

 the end of the sac nearest the micropyle. 



Mount a number of ovules in potash, then press on the 

 cover-glass with a needle so as to burst the ovules without 

 damaging the embryos which are thus isolated. If the 

 embryos are too transparent run in some acetic acid. 



With patience one can get a series showing various 

 stages in the embryogeny of this typical Dicotyledon, e.g. 

 (1) a short row of cells, at one end the elongated basal 

 cell of the suspensor, at the other the rounded embryo 

 cell ; (2) the embryo cell divided into octants, the sus- 

 pensor elongated and with greatly enlarged basal cell ; 

 (3) the octants divided by tangential walls cutting off 

 the dermatogen, the hypophysis cell of the suspensor 

 pushing in between the lower octants of the embryo, the 

 basal cell still further enlarged ; (4) the inner tissue of 

 embryonic mass differentiated into periblem and plerome ; 

 (5) the formation of periblem and dermatogen of root at 

 expense of the hypophysis cell ; (6) formation of the two 

 cotyledons by outgrowth from the upper octants, and of 

 hypocotyl from the lower ones; (7) formation of stem 

 apex or plumule between the cotyledons. 



