FOREST TREES OF THE PACIFIC SLOPE. 349 



Longevity. — Not fully determined. Like many other large tree thorns it 

 appears to be long-lived, a.s shown by its exceedingly fine-grained wood and 

 persistent growth. A tree 13§ inches in diameter showed an age of 83 years. 



A well-marked variety of this thorn, Cratcegus douglasii rivularis (Nutt.) 

 Sargent, is commonly a low shrub, sometimes nearly without thorns ; it is fre- 

 quent in western Washington and Oregon and southward to Sierra and Plumas 

 counties. Cal.. where it is less common. It is distinguished from the species 

 mainly by its narrow leaves, which are finely toothed, not deeply lobed and 

 slashed as in the species. It was described long ago as a species ( G. rivularis 

 Nuttall) am 1 is by some authors still maintained as such ; but since Intermediate 

 leaf forms are not hard to find, connecting the species over its entire range, the 

 writer believes that this form should be treated as a variety only. 



RANGE. 



From British Columbia (Tarsnip River) through Washington and Oregon to California 

 (Pitt River), and through Idaho and Montana (Flathead River at western base of Rocky 

 Mountains i. 



OCCURRENCE. 



Borders and bottoms in vicinity of lower mountain streams ; in moist, gravelly and 

 sandy soils, or in deep, rich soils i where, in Oregon, it is large). Grows in very dense, 

 large, pure thickets, patches, and small clumps, mingled with choke cherry, black cotton- 

 wood, longleaf willow, red alder, etc. 



Climatic Conditions. — Similar to those of choke cherry; adapted to very wide range 

 of conditions. 



Tolerance. — Shows signs of great tolerance ; not fully determined. 



Rbpboduction, — Very abundant seeder, and young plants numerous in shade and open 

 on borders of thickets. 



HETEROMELES. 



A genus containing but a single evergreen species which is confined to Cali- 

 fornia and adjacent islands. In general appearance it is very unlike any of the 

 other related generic groups of the family (Rosacea?), as indicated by its name 

 ( Ileteromeles). The characters of this genus are given under the species, which 

 follows. 



Christinas Berry. 



Heteromeles arbutifolia Roemer. 



DISTINGUISHING CHARACTERISTICS. 



Christmas berry, also called "California holly." " tollen," and " toyon," is best 

 known as a low shrub throughout most of its range on the mainland. In the 

 coast islands, however, especially on Santa Catalina Island, it becomes a small 

 tree from 15 to 25 feet high, but with a very short trunk from 10 to 15 indies 

 thick at the ground. The crown form of the shrub is peculiarly similar to that 

 of the tree, in which many upright branches are given off at the end of the short, 

 thick trunk. The smooth-looking, pale, ashy gray bark is indistinctly seamed, 

 and the ridges are connected. Mature leaves (fig. 164) thick, leathery, smooth 

 throughout, deep shiny green on their upper surfaces, lighter beneath, and 

 usually with two minute glandular teeth on the stem at the base of the blade. 

 Leaves of a season's growth remain on the twigs until the end of the second 



winter. The sn th. bright red berries (fig. 164), which have a dry, tart flesh, 



ripen from October to February ; they are borne in large clusters which are very 

 attractive among the glossy green leaves. line or two ridged, brown, dotted 

 seeds occur in each of the two cells of the berries. Wood, deep reddish brown, 



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