THE FLOWEErNG PLANT — LEAVES 363 



pieces of cardboard, each sufiBciently large to cover the 

 tumblers. 



Method of Excrniination. — Handle the fresh leaves as 

 little as possible, and keep in a closed box all those 

 which are not in actual use, for in some cases even a 

 short exposure to the air causes the leaf to wither. 

 Soak alcoholic material previous to examination for two 

 or three hours in a mixture of equal parts of fifty per 

 cent, alcohol and glycerine, and examine in the mixture. 



MOKPHOLOGT 



Gross Anatomy. 



Using the leafy branches of the plants named, 

 study the following : 



a. Arrangement or pJiyllotaxy. — Are the leaves ar- 

 ranged alternately or opposite to each other on 

 the stem ? If the former, tie a fine thread around 

 the base of the stalk of the lowest leaf. Eevolve 

 the stem between the fingers, and tie the thread 

 in like manner around the stalk of the second 

 leaf ; again, around the third leaf, and so on, until 

 the thread arrives at a leaf which stands directly 

 above the first. Counting from the latter, what 

 is the number of the leaf which stands over the 

 first? How many revolutions of the stem has 

 the thread made? Make a list of plants in which 

 the leaves have this spiral or alternate arrange- 

 ment. Make another list of plants whose leaves 

 are opposite. Do you find any specimens in 

 which three, four, or five leaves form a circle, 

 called a whorl or verticil, around the stem? 

 Make diagrams showing the leaf arrangement of 

 each specimen examined. 



