BETULACE^E. 4^7 



2. Alnus rubra, Bongard, I c. 



Hab. In woods, Puget Sound. In this species the leaves are 

 pubescent underneath and the veinlets connecting the primary veins 

 are more prominent than in A. viridis; the fructiferous catkins, also, 

 are thicker, and on very short peduncles. The fruit is strongly 

 winged. 



3. Alnus rhombifolia, Nutt. 



Alnus rhombifolia, Nutt, Sylv. 1, p. 33. 



Hab. Valley of the Sacramento, California, along the river; not 

 very common. This species sometimes acquires the stature of 40 

 feet, with a slender trunk 3 inches in diameter. The leaves (at least 

 when young) are nearly smooth, somewhat shining above and 

 slightly pubescent underneath, finely and doubly serrate, with the 

 serratures thickened at the tip. The fructiferous catkins are in a 

 terminal cluster and are supported on rather long but stout and rigid 

 peduncles. Scales dilated and entire at the tip, cuneate below. 

 Fruit with a thin, very narrow margin, but not winged. Nuttall 

 found this species near Monterey, but he did not detect any of the 

 fruit. There is little doubt of our plant being the same as his. Near 

 San Eafael Dr. Pickering collected specimens of an Alnus which 

 seem almost to connect this species with A. incana, var. glauca (A. 

 glauca, Michx.). The leaves are broadly ovate, obtuse or slightly 

 acute at the base, shining above, a little hairy on the veins un- 

 derneath, otherwise smooth; the serratures and fructification as 

 in A. rhombifolia. Hooker regards A. serrulate as not distinct from 

 A. incana. 



