TEHON: FIELDBOOK OF NATIVE ILLINOIS SHRUBS 11 



says, "Leaves opposite or whorled; 2 or 3 at a node." Farther 

 along in the key another line labeled B reads, "Leaves alter- 

 nate; 1 at a node." On the small dogwood branch that we 

 have at hand, leaves arranged as pairs are set opposite each 

 other on the stem. Again it is clear that our dogwood is in- 

 cluded somewhere under the first B. Under this first B, we 

 find a C line reading, "Leaf margins entire." Contrasted with 

 this, a little farther down, is the other C, "Leaf margins 

 toothed." As nearly as we can see without a hand lens, there 

 are no teeth of any kind on the dogwood leaf margins ; so we 

 follow through under the first C and come to the D lines, 

 "Leaves and twigs densely coated with silvery or rusty scales," 

 and "No silvery or rusty scales present." Finding no such 

 scales on our dogwood, we proceed under the second D to the 

 lines labeled E, "Leaf blades with translucent dots," and "Leaf 

 blades, without translucent dots." Holding our dogwood leaves 

 up to the light, we try to see any special places in the blade, 

 however minute, where the light shines through clearly. We 

 find none, and so we know that we must continue under the 

 second E. Beneath this are two lines labeled G. The first one 

 says, "Leaves often 3 at a node," the second, "Leaves definitely 

 2 at a node." If we happen to be near this shrub while we are 

 trying to name it we may examine several stems; otherwise, the 

 single stem that we have at hand will have to do, and we find 

 that there are only two and never more than two leaves at a 

 node. This carries us on under the second G. The distinction 

 between the lines labeled H is quite apparent, since the first H 

 line, which reads, "Leaves thick; parasites growing on tree 

 branches," does not at all describe our dogwood, whereas 

 "Leaves normally thin; not parasites" does at least include it. 

 So we come to the next pair of lines, labeled I, "Secondary veins 

 running together near the margins and meeting at the leaf tip; 

 leaves often mealy beneath," and, contrasted with this, "Leaves 

 without such veins; often glaucous beneath." Now, if we ex- 

 amine the dogwood leaves carefully, we shall find that sec- 

 ondary veins run out at intervals from the main vein of the 

 leaf and that, very near the margins, they run together into 

 fine marginal veins, which follow the margin of the leaf on each 

 side from the bottom secondary vein up to the tip of the leaf, 

 where they unite. This apparently is what is meant by the 

 first of the letter I lines in the key, and so we learn that our 



