PINACEAE 



The Hemlocks 

 Characteristics of the Genus Tsuga (Endl.) Carr. 



HABIT. Tall, broadly pyramidal, evergreen trees; long, 

 slightly tapering trunks; pyramidal or conical crown with 

 scattered, slender, horizontal, and often pendulous branches; 

 leading shoots characteristically drooping. 



LEAVES. Spirally arranged, often appearing 2-ranked by 

 a twist of the petioles; linear; single; abruptly petiolate; flat- 

 tened or rounded; persistent 3-6 years and leaving conspicu- 

 ous, woody, persistent bases (sterigmata) when they fall; decidu- 

 ous in drying; usually grooved above, with 2 conspicuous bands 

 of stomata below; 1 centrally located resin duct in cross section. 



FLOWERS. Monoecious, single, on twigs of previous sea- 

 son; male, or pollen-bearing, axillary, globose, of numerous 

 short stamens; female, or cone- and seed-bearing, terminal, 

 erect, of numerous, circular scales of nearly the same length 

 2is their membranous bracts. 



FRUIT. Woody, pendent cones; maturing in one season; 

 scales thin, rounded, entire-margined, several times longer than 

 bracts. Seed: 2 under each scale; small, light, and widely dis- 

 seminated; long, terminal, obovate wing; dotted with small, 

 resin vesicles. 



TWIGS. Slender; round; roughened by persistent leaf bases. 

 Winter buds; small, nonresinous, ovoid to globose. 



BARK. Rough, hard, ridged, deeply furrowed; clear choco- 

 late-red color when broken; containing tannin. 



WOOD. Moderately soft; moderately strong; resin ducts 

 normally absent; light to red-brown; considered inferior to pine 

 and Douglas-fir. 



SILVICAL CHARACTERS. Tolerant trees; requiring abun- 

 dant moisture; seldom attaining ages of more than 500 years; 

 shallow, wide-spreading root system. 



GENERAL. This genus contains 10 or more species widely 

 scattered through North America and Asia. In North America 

 there are 4 native species, 2 western and 2 eastern. 



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