FOREST TREES OF THE PACIFIC SLOPE. 407 



OCCURRENCE. 



Low river bottoms, flats, valleys, borders of slow streams (at north), and high foothill 

 slopes (southward) ; in former habitat in rich, rocky, or humous soils (best growth) and 

 in dry gravelly or sandy soils throughout southern range (here shrubby) ; abundant 

 moisture and rich soil required for largest growth. Mixed (usually as an undergrowth i 

 with Douglas fir, red alder, western red cedar, hemlock, broadleaf and vine maples, 

 Oregon crab, in alluvial bottoms, but often with manzanitas, live oaks, chaparral brush 

 elsewhere on open hill slopes. 



Climatic Conditions. — Similar to those of red alder and Douglas fir. 



Tolerance. — Exceedingly tolerant of dense shade in humid air and moist soil ; ap- 

 parently much less so in drier and exposed situations; the two habitats, different in cli- 

 matic and soil conditions, producing two very unlike forms. 



Reproduction. — Prolific seeder. Seed of medium high germination (often tardy) 

 and of very persistent vitality. Scattered seedlings fairly abundant in moist forest lit- 

 ter and mucky soils; scanty in drier habitat except in depressions where seed has 1 n 



deeply covered by accident. Growth slender in dense shade ; branched and bushy in 

 open ; shrubby in dry places. 



CEANOTHUS. MYRTLES. 



The myrtles are a small group of low, slender trees and shrubs confined 

 to North America. One eastern shrubby species is called "New Jersey tea," 

 while most of the western species are known as "lilacs" and "myrtles.'* As 

 trees they are unimportant, but as shrubs they often form a large and conspicu- 

 ous part of the useful chaparral cover on dry mountain slopes throughout the 

 western United States, where, In addition to assisting much in preventing rapid 

 run-off, a number of them furnish the principal browse in summer for range 

 cattle and sheep. The greater number of them grow in the open, but some 

 mingle with forest trees. They grow near sea level or ascend high mountain 

 slopes, frequently becoming conspicuous features in burned areas among moun- 

 tain pines, spruces, and firs. 



The twigs are smooth and unarmed (sometimes with spines or spine-pointed) 

 and frequently angled. Tlie leaves are simple (with one blade) and borne 

 singly. Prominently characteristic of the leaves, annually deciduous or ever- 

 green, are their 3 veins, consisting of the main central vein, on both sides of 

 which a vein extends from near the base of the leaf nearly or quite to'its top end 

 (figs. 194 to 196). The minute, blue or white, perfectly bisexual flowers, often 

 fragrant, occur in small, dense, branched clusters. The colored divisions 

 (petals) of the flowers resemble minute tobacco pipes. The fruits are small, 

 dry, berry-like bodies, with three rounded, bulging lobes, which are three little 

 nuts. These are joined together, but are separable when ripe; the thin, dry, 

 brittle covering of each splits open and liberates a thin, hard-shelled seed. A 

 curious fact concerning the dissemination of the seeds is that, in a number of 

 species, the seeds are quite forcefully thrown a from their outer shells. This pro- 

 vision insures their being cast upon the ground, often a little way from the 

 parent tree. Flood waters and browsing animals further assist in distributing 

 the seeds. 



Six or seven species, all found in the Pacific region, have been classed as 

 trees, but so far as can be satisfactorily determined only three of these are true 

 trees. This number is likely, however, to be increased by careful field studies 

 of some of the large, shrub-like species. 



Species of this genus are often difficult to identify in all of their variably 

 shrubby or tree forms, particularly such closely related species as ('. arboreus 

 and the shrubby ('. velutinus. Moreover, it is now known that several species 

 hybridize and so produce very perplexing forms. 



"Parry, Proc. Davenport (Iowa) Acad., v. 164. 



