114 PRACTICAL BOTANY. 



increase in thickness of the frond is effected by the divi- 

 sion of the outer cells of the cortex. Draw the entire 

 section. Test for starch. Is it present ? Run Schultze's 

 solution under the cover of another preparation. Are 

 the cell walls composed of normal cellulose ? 



4. With the hand magnifier notice the distinct notch 

 in the ends of the branches that do not bear concepta- 

 cles, i.e., those that are not swollen. Then make longi- 

 tudinal thin sections through the notches, using alcoholic 

 material. Mount in glycerine. In some of the sections 

 a well-defined four-sided apical cell will be found, sur- 

 rounded by cells which have had their origin in the seg- 

 mentation of the apical cells. Some difficulty will be 

 experienced in finding the apical cell. It is by this form 

 of cell division that the plant increases in length. Ob- 

 serve also in this section the distinction of medullary, 

 cortical, and epidermal cells. 



5. Make sections, both transverse and longitudinal, 

 through the air sacs. (Fig. 61, _Z?.) Do you find the 

 same distinctions of medullary, cortical, and epidermal 

 tissues that you have already found in the transverse and 

 longitudinal sections of the frond? Do the structures 

 found help you to judge how the air sacs were formed ? 



6. Examine with a hand magnifier the conceptacles on 

 branches that were gathered at high tide and have hung 

 about six hours in a cool place. The male and female 

 conceptacles are borne on different plants in the case of 

 Fucus vesiculosus. The male are distinguished from the 

 female by an orange-colored exudation. Notice the warty 

 appearance of the conceptacles. (Fig. 61, M.) Also the 

 ostiole, or stoma, at the apex of each wart. (This is seen 

 in section in Fig. 62, 1.) In many cases tufts of delicate 

 hairs project from the ostioles. 



7. Using alcoholic material, make thin transverse and 

 longitudinal sections through a branch bearing male con- 



