118 



TREES OF NORTH AMERICA 



yellow-green, with a slender stiff red-brown tip, and thickened entire pale margins soon 

 splitting into long slender filaments. Flowers in May and June on slender spreading more 

 or less recurved pedicels, in glabrous much-branched panicles 4-6 long, raised on stout 

 naked stem 3-7 in length; perianth ovoid and acute in the bud, when fully expanded 

 3|'-4' across, its segments united at the base into a short slender distinct tube, ovate or 

 slightly obovate, those of the outer rank usually acute, not more than half as broad as those 

 of the inner rank; stamens as long or a little longer than the ovary, with slender nearly 

 terete filaments; ovary sessile, almost terete, pale green, abruptly contracted into the stout 

 elongated style. Fruit an erect oblong capsule rounded and obtuse at the ends, tipped by 

 a short stout mucro, conspicuously 3-ribbed, with rounded ridges on the back of the car- 

 pels, Ij'-Z' long, l'-l' wide, with a thin firm light brown ligneous outer coat closely ad- 



Fig. 114 



herent to the lustrous light yellow inner coat, in ripening splitting from the top to the 

 bottom between the carpels, and through their backs at the apex; seeds 3' wide and about 

 ^2' thick, with a smooth coat and a thin brittle wide margin to the rim. 



A tree, with a rough much-branched underground stem penetrating deep into the soil 

 and a trunk often 15-20 high and 7'-8' in diameter, covered above with a thick thatch 

 of the pendant dead leaves of many years, simple, or branched at the top with a few short 

 stout branches densely covered with leaves at first erect, then spreading nearly at right 

 angles, and finally pendulous. Bark dark brown, irregularly fissured, broken into thin 

 plates, about |' thick. Wood light, soft, spongy, pale brown or yellow. 



Distribution. High desert plateaus from southwestern Texas to southern Arizona; 

 southward into northern Mexico; most abundant and of its largest size on the eastern slope 

 of the continental divide in southern New Mexico and along the northern rim of the 

 Tucson Desert in Arizona. 



DIVISION II. DICOTYLEDONS. 



Stems formed of bark, wood, or pith, and increasing by the addition of an 

 annual layer of wood inside the bark. Parts of the flower mostly in 4's and 

 o's; embryo with a pair of opposite cotyledons. Leaves netted-veined. 



Subdivision 1. Apetalse. Flowers without a corolla and sometimes with- 

 out a calyx (with a corolla in Olacacece). 



Section 1. Flowers in unisexual aments (female flowers of Juglans and 

 Quercus solitary or in spikes} ; ovary inferior (superior in Leitneriaceoe) when 

 calyx is present. 



