274 



PLANTS AND MAN 



and sprays are very similar to those of the incense cedar (fig. 193). 

 The cones are very small, being only one-half inch long, and are 

 made up of four to six pairs of thin leathery scales, two to three 

 pairs of which produce seeds. The bark is very thin and fibrous, 

 and reddish to grayish brown in color. 



Only two members of the Arbor vitae genus live in North 

 America, one native to the northeast and one to the northwest. 



Both are of some commercial im- 

 portance. The thin fibrous bark 

 and their shallow, spreading root 

 systems make them very suscep table 

 to damage by fire. 



The Northern white cedar 

 or Arbor vitae is the eastern 

 representative of the genus, inhabit- 

 ing a large part of the northeastern 

 United States and Canada and 

 extending southward to the moun- 

 tains of North Carolina. It is a 

 medium-sized tree, averaging forty 

 feet in height and two to three feet 

 thick, with a rather rapidly taper- 

 ing stem. Growth is slow, especially 

 in swamps where the tree is typical 

 in parts of its range, and old trees commonly show considerable 

 heart rot due to fungus attack, though wood is quite durable in 

 use. 



Western red cedar or giant Arbor vitae is a much larger 

 species, often reaching heights of two hundred feet and diameters 

 of ten feet. It inhabits the northern Rocky Mountains and the 

 Pacific coast from southeastern Alaska to southern California, 

 generally preferring a moist to wet habitat for best growth. In 

 youth, the growth is fairly rapid, and the trees reach sawtimber 

 size in around one hundred years. The wood is valued principally 

 for its extreme durability. 



Cypresses 



Cypresses (Cupressus) have small scale-like leaves, arranged in 

 alternating pairs and closely overlapping on the stem (fig, 194). 



Fig. 193. — Arbor vitae has 

 cedar-like foliage in a flattened 

 spray. 



