

TREES OF NORTH AMERICA 



(EXCLUSIVE OF MEXICO) 



CLASS 1. GYMNOSPERM.E. 



OVULES and seeds borne on the face of a scale, not inclosed in an ovary; 

 resinous trees, with stems increasing in diameter by the annual addition of a 

 layer of wood inside the bark. 



I. PINACE^). 



Trees, with narrow or scale-like generally persistent clustered or alternate leaves and 

 usually scaly buds. Flowers appearing in early spring, mostly surrounded at the base by 

 an involucre of the more or less enlarged scales of the buds, unisexual, monoecious (dioecious 

 in Juniperus), the male consisting of numerous 2-celled anthers, the female of scales 

 bearing on their inner face 2 or several ovules, and becoming at maturity a woody cone 

 or rarely a berry. Seeds with or without wings; seed-coat of 2 layers; embryo axile in 

 copious albumen; cotyledons 2 or several. Of the twenty-nine genera scattered over the 

 surface of the globe, but most abundant in northern temperate regions, thirteen occur in 

 North America. 



CONSPECTUS OF THE NORTH AMERICAN GENERA. 



Scales of the female flowers numerous; spirally arranged in the axils of persistent bracts; 

 ovules 2, inverted; seeds borne directly on the scales, attached at the base in shallow 

 depressions on the inner side of the scales, falling from them at maturity and usually 

 carrying away a scarious terminal wing; leaves fascicled or scattered (deciduous in 

 Larix). ABIETINE^E. 



Fruit maturing in two or rarely in three seasons; leaves fascicled, needle-shaped in 

 axillary 1-5-leaved clusters, inclosed at the base in a membranaceous sheath; cone- 

 scales thick and woody, much longer than their bracts. 1. Pinus 

 Fruit maturing in one season. 



Leaves in many-leaved clusters on short spur-like branchlets, deciduous; cone-scales 

 thin, usually shorter than their bracts. 2. Larix. 



Leaves scattered, linear. 



Cones pendulous, the scales persistent on the axis. 



Branchlets roughened by the persistent leaf-bases; leaves deciduous in drying; 



bracts shorter than the cone-scales. 



Leaves sessile, 4-sided, or flattened and stomatiferous above. 3. Picea. 



Leaves stalked, flattened and stomatiferous below, or angular. 4. Tsuga. 



Branchlets not roughened by leaf -bases; leaves stalked, flattened; not decidu- 

 ous in drying; bracts of the cone 2-lobed, aristate, longer than the scales. 



5. Pseudotsuga. 



Cones erect, their scales deciduous from the axis, longer or shorter than the 



bracts; leaves sessile, flat or 4-sided. 6. Abies. 



Scales of the female flowers without bracts; ovules and seeds borne on the face of minute 



scales adnate to the base of the flower-scales, enlarging and forming the scales of the 



cone. Seeds with a narrow marginal wing (wingless in Juniperas). 



