x USING THE KEYS 



fruit may not be in evidence, my observation that it is a climb- 

 er, leading through the sequence 1 to 2; 2 to 3, satisfies me 

 that I have seen the poison ivy, Rhus radicans, in one of its 

 protean forms. Later I may chance to find it in the grass. In 

 this guise, I should trace it through Key C (p. xxxvii as an un- 

 derbrush, coming to the same result by the steps 1 to 15 ; 15 to 

 37; 37 to 38; 38 to 53; 53 to 54; or 1-15-37-56. In its bushy 

 southern form, and with more lobed leaves, I should trace the 

 scarcely separable poison oak, R. Toxicodendron, through Key 

 B (p. xxi) by the steps 1-35-66-67-155, where I get a cautionary 

 signal; 155-156-157-158. In addition to learning this dangerous 

 plant, I may have satisfied myself incidentally that the harm- 

 less Virginia creeper can be distinguished from it by having 

 5 leaflets in. each leaf, and by climbing by tendrils opposite the 

 leaves. 



An entomologist conies to me with a branch of a tree badly 

 infested with scale insects. He thinks that he knows the tree, 

 but wishes to be sure of it because the owner and his neigh- 

 bors can not say what it is. The Synopsis of Groups leads me 

 to Key A (p. xiii). It is obviously deciduous, not at all prickly 

 or spiny, with rounded twigs, opposite leaves that are rather 

 large, and pinnately compound with five or seven somewhat 

 toothed short-stalked leaflets, green on both sides. Through 

 Key A, I go by the successive steps 1-33-46-117-126-127-128, 

 where I find that the scars from which last year's leaves have 

 fallen are squared off below this year's twigs or any undevel- 

 oped buds of last season, so that I am convinced that it is a 

 Fraxinus. In the keys to the species of ash (p. 127) I go 

 successively from 1 to 2; 2 to 11; 11 to 14, where I find it to 

 be Fraxinus lanceolata. Reference to the Cyclopedia gives 

 fuller information about the tree, which in parts of the west 

 is being exterminated, like lilacs, dogwoods, willows etc., by 

 an oyster-shell scale. 



Under some shrubbery, I see very often a trailing little 

 evergreen with lanceolate or elliptical entire simple leaves, two 

 at a node (opposite) ; and its single large blue flowers attract 



