34 BULLETIN 863, IT. S. DEPARTMENT OE AGRICULTURE 



To use the key, decide first, by an examination of the leaf, in which of the 

 following seven sections your tree belongs; then turn to that section, and from 

 the descriptions there given determine what kind of tree it is. 



Section 



Trees with needles or scalelike leaves, mostly evergreens, bearing cones I 



Trees with broad leaves : 

 Leaves simple — 



Alternately attached to twigs — 



With toothed edges II 



Edges neither toothed nor notched III 



Opposite on twigs — 



With toothed edges IV 



Edges neither toothed nor notched. _~ V 



Leaves compound — 



Alternately attached to twigs VI 



Opposite on twigs VII 



THE CONIFEROUS 2 TREES 



I. Trees with Needle or Scalelike Leaves, Mostly Evergreen, Bearing 



Cones 



A. Leaves needle-shaped: 



(1) Leaves clustered — 



(a) Leaves long, from 1 to 18 inches, 2 to 5 in a cluster. Cones 



large, with many thick, woody scales (Pinus) Pine. 



(b) Leaves short (less than 2 inches long) in brushlike clusters 



of 12 to 40, falling off in late autumn or early winter. 

 Cones very small, with thin scales, remaining on tree for 

 one or more seasons (Larix) Larch. 3 



(2) Leaves single — 



(a) Leaves scattered around twigs; falling off when dry or dead. 



Cones elongated, with thin scales. Twigs roughened by 

 leaf -scars. 



(x) Leaves stiff, often sharppointed and more or less 



f oursided (Picea) Spruce. 



(y) Leaves soft, flat, rounded, or notched at ends, the 

 bases abruptly contracted into threadlike 

 stems (Tsuga) Hemlock. 



(b) Leaves in two distinct rows, one on each side of the twig; 



falling off in late autumn or early winter. Cones small, 

 ball-like (Taxodium) Bald cypress. 



(c) Leaves often in two rows on the sides of the twigs of lower 



branches and mostly flat, those on upper branches stouter 

 and arranged on the sides and tops of the twigs. Cones 

 long, erect, produced only on upper side of topmost 

 branches; the scales falling off in autumn, leaving spike- 

 like central axes of the cones attached (Abies) Fir. 



B. Leaves scalelike, pointed, overlapping, closely forming flat or four-sided 



twigs. 



(1) Twigs four-sided. Cones spherical or ball-like, with small, thick 



scales armed with a spurlike point; seed with very narrow, hard 

 wings ^ (Cupressus) C vpress . 



(2) Twigs flattened. 



(a) Cones elongated, with only a few thin scales; bent back on 

 branches (Thuja) Arborvitae. 



(6) Cones spherical, very small, berrylike, with thin scales 

 armed with a tiny point; seeds with a broad, thin wing 

 on two sides (Chamsecyparis) Cedar. 



(c) Cones berrylike (showing indistinct outlines of, but no 

 separation into, scaly parts). Leaves either short, scale- 

 like, and sharpjointed, or much longer, needlelike, standing 

 out loosely, and attached in pairs or in threes on the 

 twigs (Juniperus) Juniper. 



2 Cone-bearing. 



3 The larches are peculiar in having single, scattered leaves on the new or terminal twigs produced each 

 season. These should not be mistaken for the "single" leaves borne throughout by other kinds of ever- 

 greens. 



