HOW TO USE KEYS xi 



carp a". This determination is then checked by turning to pages 

 264 and 265, where the description and illustration of the species are 

 found. 



If the pine is taken for determination, the choice first falls upon 

 "1. Leaves needle-like or scale-like". The pine with its needles in 



III. Leaf Edges. 



12 3 4 5 6 



1. Serrate (saw-toothed). 2. Dentate (tooth- 

 ed). 3. Crenate (scalloped). 4. Undulate 

 (wavy). 5. Sinuate (bayed). 6. Incised 

 (jagged). 



groups of 2-5 then goes in "i. Leaves alternate or fascicled", and 

 beneath this, not in "a", but in "b. Leaves or some of them fascicled". 

 Under this, the few evergreen leaves in a fascicle lead one to "(2) 

 Leaves persistent, 2-5 in each fascicle" . . . Pinus : pine". On 

 page 30 is found the description of the pine genus, and below this the 

 key to the various pines. The five needles of the white pine at once 

 determine this to be Pinus St rob us, while the pines with two 

 needles in a fascicle may be sought in the general key on page 32, or 

 in the key based upon leaf-sections, page 31. 



12 3 4 5 6 



1. Acuminate. 2. Acute. 3. Obtuse, 



tuse. 6. Emarginate. 7. Obcordate. 



cronate. 



In the case of flowering twigs, the method of finding the name is 

 essentially similar. The lilac, for example, in the "Flower Key to 

 the Families", falls under "I. Petals present", the alternative choice, 



