CAPSELLA. EMBRYO. Io3 



To study the structure of the embryo, either longitu- 

 dinal sections of the ovule must be cut, and the embryo be 

 thus laid bare, or the embryo must be removed from the 

 ovule. The former is the more accurate method, though 

 the latter is much the easier : we will therefore adopt 

 the latter. 



Press gently with a needle upon the cover slip of 

 the above preparation, so as to burst the ovules : the 

 embryo will escape in some cases without injury ; 

 neutralise the potash with dilute acetic acid. The 

 structure of the embryos, which now lie freely suspended 

 in the fluid, may be easily studied. 



Apply the same method for the preparation of 

 embryos, from ovaries of various ages, both younger 

 and older than that first taken. A series of prepar- 

 ations may thus be obtained illustrating various stages 

 of' development of the embryo, such as are figured in 

 ordinary Text-books. 



Note more especially the following successive stages 

 of development : 



1. The Suspensor, consisting of one or more cells, 

 and terminated by a single Embryonic cell. 



2. The embryonic cell divided into octants arranged 

 in two tiers, the terminal cell of the suspensor 

 (Hypophysis) encroaching between the four lower 

 octants. 



3. The octants so divided up as to form three layers of 

 cells, which have been distinguished as (a) the external 

 Dermatogen ; (b) the Periblem ; (c) the central 

 Plerome. 



4. The two Cotyledons formed by lateral outgrowth 

 from the upper tier of octants, the apex of the Radicle 



