THE SILVA OF COLORADO II5 



Family PINACEAE,^ Pine Family 



Trees and shrubs with needle-like foliage leaves; usually resinous. Flowers 

 appearing in spring, strobillate. Staminate strobili relatively small, consisting of 

 numerous microsporophylls borne on an elongated axis, the pollen sacs producing 

 a large quantity of pollen. Carpellate strobili consisting of spirally arranged cone 

 scales each accompanied (in most cases) by a bract which is shorter or longer than the 

 scale. Cone scales becoming woody or papery at maturity. Seeds with straight 

 embryo embedded in copious endosperm. 



Key to the Colorado Genera of the Pine Family^ 



A. Foliage leaves (needles) in bundles of two or more surrounded at base by a short 

 sheath. Leaves mostly more than 25 mm. (i in.) long. Cones hard and woody 

 when mature. i. Genus Pinus 



(See the Key on p. 116) 



B. Foliage leaves (needles) solitary, not in bundles; mostly less than 25 mm. (i 



in.) in length. Mature cones leathery or papery; not hard and woody. 



a. Leaves jointed near the base, the lower part of the leaf brown and woody 

 and remaining on the branchlet after the rest of the leaf has fallen. Leaves 

 in our species stiff and four angled; not flat. Cones pendulous. 



2. Genus Picea 

 (See the Key on p. 119) 



b. Leaves not brown nor woody at base, flat. When they fall off they they 

 leave a scar but no part of the leaf remains. 



a' Leaves rather soft; narrowed toward the base into a short stalk which 

 broadens slightly at the point of attachment. Leaf-scars transversely 

 elliptical. Cones pendulous, the projecting bracts three-pointed. 



3. Genus Pseudotsuga 



(See the Key on p. 120) 



b' Leaves somewhat stiff, not narrowed at base; leaf scars rather large, 



circular in outHne. Cones erect, dark purple or blackish or sometimes 



yellow. 4. Genus Abies 



(See the Key on p. 122) 



Genus PINUS, The Pines 

 Evergreen trees and shrubs, growing often in dry and rocky soil; wood of most 

 species valuable for timber. Bark thick and furrowed. FoHage leaves needle- 

 shaped, in bundles usually of 2 to 5 leaves or in some species 6 or 7; rarely single. 

 The foliage leaves are borne on very short twigs (dwarf shoots) , which arise in the 

 axils of appressed scale leaves and are surrounded at the base by a short sheath. 

 Flowers monosporangiate; the staminate clustered at the base of leafy shoots of 

 the same year. Stamens (microsporophylls) very many, spirally arranged. Car- 



' In addition to the works previously cited the author has consulted for the technical descriptions 

 A Handbook of the Trees oj California by Miss Alice Eastwood and "The Conifers of Vancouver Island," 

 by F. K. Butters in Postelsia, the yearbook of the Minnesota Seaside Station, pp. 135-212, 1906. For 

 the use of a copy of the former book he is indebted to Miss Eastwood and to Miss Alice Phelps, a student 

 of the University of Colorado. 



' The cedars and junipers are not included here. A later paper will be devoted to them. 



