§ USING THE KEYS, 
that there are three species with only 3 leaflets to each of the 
compound leaves; although the characteristic white fruit may 
not be in evidence, my observation that it is a climber, leading 
through the sequence I 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. 34) as an underbrush, coming 
to the’ same result by the steps 1 to 15; 15 t0 36; 3a.to 340; 
39 to 54; 54 to 55. In its bushy southern form, and with more 
lobed leaves, I should trace the scarcely separable poison oak, 
R. Toxicodendron, through Key B (p.19) by the steps I to 33; 
33 to 61; 61 to 62; 62 to 149; 149 to 150; 150 to 151, where | 
get a cautionary signal; 151 to 152. In addition to learning 
this dangerous plant, I may have satished myself incidentally 
that the harmless Virginia creeper can be distinguished from 
it by having 5 leaflets in each leaf, and by climbing by tendrils 
opposite the leaves. 
An entomologist comes 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 neighbors 
can not say what it is. The Synopsis of Groups leads me to 
Key A (p. 11). 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 I to 26; 26 to 39; 39 to 104; 104 to 
112. Here I cut the twig cleanly across midway between two 
nodes and find that the pith is of moderate diameter as com- 
pared with elder-pith; and the succeeding steps are 112 to 113, 
and 113 to 114, where I find that the scars from which last 
year’s leaves have fallen are squared off below this year’s twigs 
or any undeveloped buds of last season, so that I am convinced 
that it is a Fraxinus. In the key to the species of ash (p. 158) 
I go successively ‘from 1 to 2; 2 tO. 3; 3 tO 10; abe mere 1O 
14, where I find it to be Fraxinus lanceolata. Reference to the 
Cyclopedia gives fuller information about the tree. 
