122 PRACTICAL BOTANY 



work. Treat with dilute potash, and examine with a low 

 power. Observe 



1. The form of the ovule (campylotropous, i.e. with a curva- 

 ture of the body of the ovule). 



2. The funiculus, or stalk. 



3. The integuments. 



4. The micropyle, not very easily seen : a pollen-tube may 

 often be observed entering the micropyle. 



5. A large central cavity (the embryo-sac), which is curved 

 like the whole ovule. In this may be seen, more or less 

 distinctly 



6. The embryo. 



To study the structure of the embryo, either longitudinal 

 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 : the latter will therefore be adopted. 



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 ; but this will only be the case 

 when fresh material has been used ; after hardening in alcohol 

 the embryos will not readily leave the ovule. Neutralize 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 preparations may thus be obtained illus- 

 trating 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 suspensor is elongated and the cells divided so as to 

 form a series, of which the basal cell (that nearest the micro- 

 pyle) is usually enlarged greatly, so as to exceed the embryo in 



