THE CELL 27 
fluid called Latex. These tubes are known as Latt- 
CIFEROUS CELLS and often branch extensively, forming 
a complete network. 
PRACTICAL EXERCISES ON CHAPTER II. 
1, Mount in water a few filaments of Spirogyra, and sketch 
a single cell showing 
(a) The cell wall; 
(b) The spiral chlorophyll body ; 
(c) The cytoplasm and nucleus. 
2. Cut a section of a bean seed. Mount it under the low 
power and note the cells packed full of starch grains. Make a 
sketch of same. 
5. Do the same with the castor-oil sced. 
4. Place a small drop of growing ycast on a slide and examine 
with the high power. Sketch a single cell showing the cell 
wall, protoplasm, and vacuoles. 
5. Boil a green leaf in water for a few minutes and then steep 
it in warm alcohol or methylated spirits until all the chloro- 
phyll has been extracted from it. Note the colour of the leaf 
so treated. Also examine the nature of the green soli tion 
obtained. 
QUESTIONS ON CHAPTER II. 
1, Explain how a xylem vessel and a sieve tube differ in 
(a) Their structure ; 
(b) Their function ; 
(c) The way they are formed. 
2. Mention three substances commonly met with in large 
quantities in plants as reserve materials. Give examples of 
plants in which you have noted these substances, and state 
(a) in what part of the plant they are found ; and (6) how you 
would demonstrate their presence. 
3. Describe the principal kinds of parenchymatous and of 
prosenchymatous tissues. Illustrate the descriptions by means 
of diagrams, and state in which parts of plants these tissues 
occur. 
4, What is cell sap? Where does it occur and what does it 
