40 REPRESENTATIVE PLANTS 



4. Take a vigorous geranium, or better a primula obconica 

 (baby primrose). Water well, wrap the whole pot and top 

 of soil in tin-foil, making a tight joint about the plant 

 stem, then carefully weigh and balance on a pair of scales. 

 Record the results from day to day. What is it that the 

 plant is giving off that affects its weight, and where does 

 this substance come from to the plant? Through what 

 plant structures does it reach the leaves ? 



Read " Transpiration " and hud out its value to the plant, 

 and in particular, how it is regulated. Try experiment 5. 



5. Place fresh leaves of mullein and lettuce on the table 

 for one hour and observe the results. Whicli wilts more 

 rapidly? "What explanation is there ? 



6. Take a vigorous geranium having several healthy leaves. 

 Inclose a young leaf in black French tissue paper. Place 

 the plant in the sunlight, and after three days test this 

 leaf and another similar but uncovered leaf for starch. 

 (Remove the chlorophyll with alcohol.) Which leaf shows 

 a starch reaction ? The process of starch making in leaves 

 or other green parts is pliotofiyntliesis. Read about this in 

 reference books. (See algae studies.) 



7. Take a vigorous leaf from a geranium near the close of a 

 sunny day, take out the chlorophyll, and test for starch. 

 Take another from the same plant in the early morning, 

 before any sunlight has affected it, and treat as before. 

 Explain the results. 



8. Experiments on respiration are difficult, and the pupil 

 may read about this function. 



Record carefully each experiment performed above, or 

 any other introduced by the instructor or ivorked out by 

 yourself. Where possible, make diagrams to show ap- 

 paratus. 



9. Take a geranium shoot and i)lace cut end in a weak 

 eosin solution. Examine the leaf after a day or two, and 

 observe the location of the color, and explain. 



