198 STORAGE OF FOOD AND WATER 



285) arid mount them in a drop of dilute glycerine. The oil 

 will be stained pink. Notice how it gathers in droplets of various 

 sizes around the edges of the section, and the abundance of it 

 in the uninjured cells. 



4. Test the endosperm of germinating and ungerminated castor 

 bean for glucose (see under Copper Acetate and Fehling's solu- 

 tion in Chapter XVI). How do you interpret the results? 



5. Examine with a high power in a drop of water starch 

 from ungerminated and germinating barley. What evidence do 

 you find that starch is digested during germination ? 



Test both germinating and ungerminated barley for glucose 

 by crushing the grains and boiling them in Fehling's solution. 



6. Cut free-hand or on a sliding microtome cross and longi- 

 tudinal radial and tangential sections of grape stem. Mount 

 the sections in glycerine-iodine (see under Glycerine and Iodine 

 in Chapter XVI). Note the extent of the storage of starch and 

 proteids in phloem, medullary rays, and wood parenchyma. 

 Other woody stems will do, but the grapevine is especially fine 

 for showing this. Make drawings from each region of a few 

 cells with contents. 



7. Make thin cross sections of rubber leaf and mount them 

 in dilute glycerine. Note the clear tissue between the epider- 

 mis and palisade cells. This is for the storage of water. Make 

 a diagrammatic drawing of the leaf expressing the proportion of 

 leaf devoted o water storage. 



8. Cut tangential sections (see Chapter X, page 173, par. 2) 

 of a sunflower leaf and mount them in dilute glycerine. The 

 large clear cells are water-storage cells. Draw a few of these 

 cells with the surrounding mesophyll tissue. 



