218 



BOTANY FOR BEGINNERS 



CHAP. 



suspensor. (Fig. 214) The outer cells of the embryo, as it can 

 be called, divide up to form the dermatogen (p. 112), which 



forms the whole epi- 

 dermis of the plant. 

 The inner cells divide 

 up to form the picromc, 

 from which the central 

 cylinder of the main 

 stem is formed. Cells 

 are produced between 

 the dermatogen and 

 plerome, from which 

 the cortex is produced. 

 These form the peri- 

 blem. 



EXPT. 189. From the 

 Shepherd's Purse pull off 

 a number of ovaries in 

 different stages of deve- 

 lopment. Remove the 

 wall from a young ovary, 

 and with needles separate 

 some of the ovules from 

 the replwn or central 

 dividing wall of the ovary. 

 Soak some of the ovules 

 in potash solution for ten 

 minutes, or until they are 

 almost transparent. 



Mount them in a drop 

 of glycerine on a slide and 

 place on a cover-glass. 

 Press, or give the cover- 

 glass a sudden tap, to 

 burst the ovules and force 

 out the embryos. Use the 

 low power for the older 

 stages and for the younger 

 ones the high power. 

 Note 



(i) The suspensor, which 

 consists of several cells, at 

 the end of which the em- 

 bryonic cell will be seen. 



(ii) The embryonic cell in an older specimen will have divided into a 

 number of cells. 



J) 



FIG. 214. Stages in the development of embryo of 

 the Shepherd's Purse, c,. cotyledons \p, plumule ; 

 et, suspensor ; A, hypophysis. (Magnified.) (S.) 



