132 PRACTICAL BOTANY. 



II. Pick out gently a number of ovules from an 

 ovary of a flower of Datura Stramonium, which has 

 just faded, and mount in dilute glycerine. Observe 



1. The Campylotropous Ovules, with curved body. 



2. Pollen-tubes, which are often to be found with 

 the end applied closely to the micropyle. 



Strasburger observed the process of fertilisation itself directly 

 in Torenia asiatica, Gloxinia, and also in Orchids, Monotropa, and 

 Pyrola. His method was to open the ovary of a flower a short 

 time after pollination, and detach and mount the ovules in a 3 per 

 cent, solution of sugar. 



DEVELOPMENT OF THE EMBRYO. 

 i. Dicotyledon. 



Pick out the ovules from an ovary of Capsella Bursa- 

 pastoris, which has attained about half the ultimate 

 size of the mature fruit. Treat with dilute potash, and 

 examine with a low power. Observe 



1. The form of the ovule (campylotropous, i.e. 

 with a curvature 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. 



