BETULACEAE. 25 
Atnus. Alder. 
(Family Betulaceae). 
Typically shrubs: deciduous. 
Bark smoky or gray, smooth or 
fissured in rather large or scaly 
areas. Twigs often 3-sided: pith 
small, 3-sided, continuous. Buds 
rather large, solitary, usually 
stalked, with 3 subvaivate scales. 
Leaf-scars alternate, half-round, 
somewhat raised: bundle-traces 
3, or the lowest compound: §sti- 
pule-scars narrow. 
Alders are particularly interest- 
ing in winter through having 
their buds-~ distinctly stalked. 
Though this character is by no 
means limited to them, nor do 
they all show it, there are few 
genera in which it is so readily 
observable. Their fruit is also 
persistent in the form of small 
cone-like bodies, which differ in 
shape and position in different species, and as a rule the 
staminate catkins for the next. season are conspicuous. 
1. Buds stalked. 2. 
Buds sessile: bushes. 5. 
2. Very tree-like. (European alder). A. glutinosa. 
Bushy, even when large. 3. : 
3. Bud-scales narrow and separated. (1). A. maritima. 
Bud-scales valvate. 4. 
4. Fruiting cones erect. (Smooth alder). (2). A. rugosa. 
Fruiting cones pendent. 
(Speckled alder). (3). A. incana. 
5. Twigs glabrescent. (Mountain alder). A. crispa. 
Twigs hairy. (Downy alder). A. mollis. 
