a. Houses wood. 



t>. Body paint brown Smith's house 



bb. Body paint white. 



c. Trimmings green color Jones' house 



cc. Trimmings slate color Brown's house 



aa. Houses brick. 



b. Roof gray slate Johnson's house 



bb. Roof red tile .Public Library 



It is desirable in many cases to add other characters to 

 lessen the liability of confusion, where the characters chosen are 

 not distinct, and to show the user that he is on the right track. 

 Thus, in the example just given, green color and slate color under 

 certain defects of the eye, a coating of dust or deficiencies of the 

 light might be confused, under which circumstances we would be 

 justified in adding to the above statements without the criticism 

 of description being made. Thus : 



bb. 



c. Trimmings green color; gable roof. Jones' house 



cc. Trimmings slate color; mansard roof Brown's house 



The keys in this bulletin are constructed on the above prin- 

 ciples. They are not in all cases as simple as the illustration just 

 used, but if the reader has mastered the house illustration he 

 will have little or no trouble with the larger keys. Suppose that 

 (during a summer stroll) you come across a large tree with 

 rough, hard bark and thin, lobed leaves which you do not know. 

 Turning to the Summer Key to the Genera you find first a. 

 Leaves simple, and contrasted with this aa. Leaves compound. 

 Obviously the leaf is simple and tihe genus sought lies in that 

 portion of the key preceeding aa, i. e., under a. b and bb under a 

 give you a choice between Leaves needle-shaped, awl-shaped, 

 strap-shaped or scale-like and Leaves broad and flat. The leaf 

 being broad and flat you pass to c and cc under bb. Here you 

 have a choice between Leaves alternate or clustered and Leaves 

 opposite or whorled. Inspection shows the arrangement to be 

 opposite, and you know that the genus sought lies in that portion 

 of the key between cc and aa. Passing to d and dd under cc 

 gives the choice between Margin of leaves entire or only slightly 

 undulate and Margin of leaves serrate, toothed or lobed. ' The 

 xix 



