78 STUDY OF COMMON PLANTS. 



of them will soon show formation of pollen-tubes. Draw 

 them in different stages of development.^ 



III. Cut transverse sections of the ovary of Trillium at 

 the time the flower is fading and at subsequent periods. 

 Under the compound microscope study the ovules in 

 different stages of growth. Notice 



1. The anatropous form of the ovule. 



2. Its two coats distinctly marked at the apex. 



3. The nucellus, or mass of tissue making up the body 



of the ovule. 



4. The micropyle, a canal leading from the apex of the 



ovule to the nucellus. 

 Draw and describe. 



IV. Prepare similar sections of the ovary of Fuchsia, 

 Begonia, and various other plants, studying carefully, as 

 before, the structure of the ovule. Some of these will 

 show, lying within the nucellus, the outlines of the embryo- 

 sac, a large cell in which the embryo is subsequently 

 formed. Clearing with potash solution facilitates the 

 observation. Indian-pipe, Monotropa uniflora, L., when 

 it can be obtained, is an extremely favorable species for 

 the study of the embryo-sac and the structures contained 

 in it.^ 



V. Take a flower-bud of shepherd's-purse, Oapsella 

 Bursa-pastoris, Moench, and under a lens remove the floral 

 envelopes. Open the ovary and dissect out the ovules. 

 Treat on the slide with dilute potash solution and apply 

 light pressure to the cover glass. If a series of younger 



1 For further hints as to culture methods, of. Strashurger, Practical 

 Botany, p. 320 c ; Halsted, Bot. Gaz. XII (1887), p. 287. 

 a Cf. Strashurger, I.e., pp. 327-337. 



