BETULACEiE. 



139 



Sierras at considerable elevations. An infrequent tree in the Coast 

 Ranges of middle California: Mitchell Canon, Mt. Diablo; San 

 Leandro Creek; Carnadero Creek, near Gilroy, Jepson; no other 

 localities in the Bay Region hitherto recorded; noted near the Moun- 

 tain House on the Round Valley road from Ukiah and at occasional 

 stations northward but rarely. Winter buds over \ in. long, very 

 slender and long-pointed. Sometimes called "Balsam Cottonwood." 



P. tremuloides Michx., the Aspen of the High Sierras, has 

 round-ovate leaves, crenulate or almost entire, abruptly acuminate, 

 1 to \\ or 2 in. long; 7 to 10 stamens; and linear stigmas. 



15. BETULACE/E. Birch Family. 



Trees or shrubs with alternate petioled simple leaves, caducous 

 stipules, and small flowers in linear or elongated clustered aments. 

 Staminate aments pendulous, the flowers in clusters of 3 in the axil of 

 each bract, consisting of a membranous 4-parted calyx and 2 to 4 

 stamens. Pistillate aments much smaller, erect, spike-like, the 

 flowers 2 in the axil of each bract, without perianth, consisting of a 

 pistil with two styles and a 2-celled ovary with 1 ovule in each cell; 

 fruit a small compressed 1-seeded nut which i- margined or winged. 



1. ALNUS L. Alder. 

 Our trees with toothed leaves and aments which appear in the 

 autumn of the year previous to their flowering and pass the winter 

 naked. Bracts of the staminate anient dilated above with the apex 

 abruptly upturned, each covering 4 bractlets. Pistillate aments 

 woody and cone-like when mature, the bracts and bractlets united 

 and persistent. (So called on account of the trees growing along 

 streams, the name derived from the Celtic through the Latin.) 



Bracts of staminate ament acute; stamens 4 1. A. Orepana. 



Bracts of staminate ament obtuse; stamens 2 to 4 2. A. rhombifolia. 



1. A. Oregana Xutt. Red Alder. Tree 30 to 45 ft. high, the 

 limbs long and straight and the ultimate branchlets mainly few; 

 trunk usually £ to 1£ ft. in diameter, gray or almost white and often 

 mottled; leaves broadly ovate, 2 to 6 in. long, more or less pubescent 

 and often rusty beneath; the margin irregularly serrulate and some- 

 times more or less revolute, the teeth callous-tipped and mostly 

 triangular or blunt; staminate aments 3 to 5 in. long; bracts acute; 

 stamens 4, filaments less than 1 line long, the anthers brick-red; 

 pistillate aments 6 lines long; cones oblong-ovate, | to 1 in. long; 

 bracts with the apices turned abruptly upward and, therefore, slightly 

 tabular at summit; nutlets winged, 1 line long. — (A. rubra Bong.) 



Bottoms of canons along streams in the Coast Ranges throughout 

 the State. Feb.-Mar. 



2. A. rhombifolia Nutt. White Alder. Tree 20 to 35 ft. 

 high with trunk of a light-gray or ashy color, mottled with large 

 blotches, the limbs often ultimately much branched and becoming 



