■ 



Introduction 



HOW TO USE THE KEY 



The method of using the keys for finding the names of plants may he shown best by taking a 

 common (lower as an example. If we choose the morning glory for this purpose, we turn to the 

 "Key to Families" on page \i. Here it is necessary to decide first whether the petals are present 

 or absent. Since petals and sepals are both clearly present, choice is made of "I. Petals present." 

 Under this heading it is then necessary to decide between "1. Flowers single or in clusters," and 



I. Leaf Outlines 



1. Rounded. 2. Cordate (heart-shaped). 



6. Sagittate i arrow-shaped '. 



3.4. Reniform (kidney-shaped). 5. Peltate (shield- shaped). 



7. Auriculate (eared). 8. Hastate (halberd-shaped). 



"2. Flowers in heads." Examples of the latter are clover, sunflower, asters, etc. The morning 

 glory evidently falls under "1." The next choice is between "a. Petals 3," and "b. Petals 4 or more." 

 Since the morning glory has five petals grown into a funnel-shaped tube, "b" is chosen, and the 

 decision then rests between "(1) Petals separate" and "(2) Petals united" and then under "(2)" 

 between "(a)"' Ovary superior, i. e., within the other parts," and "(b) Ovary inferior, i.e., below 

 the other parts." The ovary is found within the corolla tube and is consequently superior. An in- 



II. Leaf Outlines and Bases 



' 



1. Linear. 2. Lanceolate (lance-shaped). .V Oblong 4. Elliptic. 5. Oval. 6. Ovate i egg-shaped). 



7. Oblanceolate. 8. Spatulate ispatula-likeV 9. Obovate (reversed ovate). 



10. Cuneate (wedge-shaped). 



ferior ovary is found at the bottom of the calyx and corolla, as in the iris, the honeysuckle and the 

 single flowers of dandelions, asters, etc. It is next necessary to know the number of rooms or cells 

 in the ovary. This can be told readily from the ripe fruit as a rule, or from cutting a cross section 

 of the ovary. If there are no cross walls, the ovary is one-celled. In the morning glory, the ovary 

 is divided into three cells so that choice is first made of "z. Ovary 3-celled," in place of "x. Ovary 

 one-celled," or "y. Ovary 2-4 celled," fitting the plant in hand. Under "a" we find "(x) Twiners," 



