160 LABOR A TOE Y AND FIELD EXERCISES 



how many rows of ovules or megasporangia ? Deter- 

 mine this point by gross studies of the external 

 features of the pistil, and by examining gross trans- 

 verse sections of the pistil made with a scalpel or 

 safety-razor blade. 



b. Draw a lateral view of the pistil and a transverse section 

 of the ovary. Label the parts in terms of megasporo- 

 phylls (carpels) and megasporangia (ovules). 



2. Megasporangia, or ovules. Dissect out a considerable 



number of ovules from both young and mature ovaries 

 on a slide in a drop of water. Eemove half of the 

 ovules to a second slide and mount in a weak potash 

 solution. Cover and study your two preparations to 

 determine the following points : 



a. Parts of the meyasporangium, or ovule. Observe the 



funiculus, ovule proper, integuments, and micropyle. 

 The embryo sac may often be seen in outline in 

 specimens treated with potash. Compare the form 

 of young and mature sporangia and note the gradual 

 curvature of the entire sporangium and spore as the 

 ovule matures. 



b. Embryo sporophyte. The embryo can often be seen, in 



specimens bleached in potash, lying above the micro- 

 pyle. It may be obtained free on the slide by slight 

 pressure on the cover glass. 



c. Drawings. Draw the ovules of Capsella to show as 



many of the above structures as you have been able 

 to demonstrate, including the embryo and its parts. 

 Name all parts correctly, consulting the text figure 

 and the description of parts there represented. 



3. Female gametophyte and sporophyte of Capsella. Study 



the female gametophyte, embryo sac, and sporophyte 

 in prepared slides of ovaries of Capsella. Work out as 



