a. Houses wood. 
b. Body paint brown............... 0.000000 Smith's house 
bb. Body paint white. 
c. Trimmings green color.............0..0005 Jones’ house 
cc. Trimmings slate color...............0.05 Brown’s house 
aa. ‘Houses brick. 
be ROL pray Slaten s cocci ods qaedavadnlvndies Johnson’s house 
bb. Root £60: Me: 4s. eeigex ccus gan bacco 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. 
ce. 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 the genus sought lies in that 
portion of the key preceding aa, i. e., under u. 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 to lobed. ‘The 
— xIx — 
