THE SILVA OF COLORADO 55 
BETULACEAE, BrircH FAMmILy 
Alnus tenuifolia Nutt. ALDER 
A small tree along streams throughout the plains and foothill regions. 
Altitude: 5,000 to 10,000 ft. Collections: East of Boulder; St. Vrain Creek; Sun- 
shine Canyon; South Boulder Canyon; Allenspark; Eldora; west of Ward; “lower 
Boulder Canyon’”’ (Rydberg). 
Betula andrewsii Aven Nelson. BIRCH 
A small tree resembling the paper birch of the eastern states. Known only from 
Green Mountain near Boulder. 
Betula fontinalis Sarg. CANYON BIRCH 
A handsome tall shrub or small tree with shining leaves. Along watercourses. 
Altitude: 5,250 to 10,000 ft. Collections; St. Vrain Creek; Bear Canyon; South 
Boulder Canyon; Allenspark; Sugarloaf Mountain; foot of Long’s Peak; “Eldora to 
Baltimore”? (Rydberg). 
Betula glandulosa Michx. Swamp BircH 
A shrub about 1 meter high growing in mountain bogs and along streams. 
Altitude: 8,500 to 11,000 ft. Collections: Redrock Lake; west of Ward; Goose 
Lake near Arapahoe Peak; Bald Mountain; “Eldora to Baltimore” (Rydberg). 
CORYLACEAE, Hazet-Nut Famity 
Corylus rostrata Ait. HaAzEL 
A tall shrub growing in clumps. 
Altitude: 5,500 to 8,000 ft. Collections: Gregory Canyon; South Boulder Canyon; 
Sugarloaf Mountain; “lower Boulder Canyon” (Rydberg). 
ULMACEAE, Etm Famty 
Celtis reticulata Torr. HAcCKBERRY 
This is C. occidentalis of Coulter’s Manual. An elm-like tree of exposed ridges and 
foothills. Rather rare in Boulder County. 
Altitude: 5,600 to 6,500 ft. Collections: Valmont Butte; Sunshine Canyon; gulch 
near Boulder Cemetery; “plains and foothills near Boulder”? (Rydberg). 
CANNABINACEAE, Hemp Famity 
Humulus lupulus neo-mexicanus Nels. and Ckll. Mountain Hops 
Trailing on the ground or over bushes and rocks in shaded situations. 
Altitude: 4,900 to 8,000 ft. Collections: Near Boulder; Sugarloaf Mountain. 
LORANTHACEAE, MIstLEeEToE FAMILY 
Razoumofskya americana (Nutt.) Kuntze. MISTLETOE 
Parasitic on the lodgepole pine. 
Collections:' Sugarloaf Mountain; near Rollinsville; near Pine Glade School; 
“Sunset” (Rydberg). 
Razoumofskya cryptopoda (Engelm.) Kuntze. MISTLETOE 
Parasitic on the rock pine, often causing the formation of so-called “‘ witches’ brooms.’” 
Collections: Mt. Alto Park; “Between Sunshine and Ward” (Rydberg). 
