CUPULIFERE. SILVA OF NORTH AMERICA. 37 
OSTRYA KNOWLTONI. 
Ironwood. 
LEavEs oval or obovate, acute or rounded at the apex. 
Ostrya Knowltoni, Coville, Garden and Forest, vii. 114, f. 23 (1894). 
A tree, from twenty to thirty feet in height, with a trunk from twelve to eighteen inches in 
diameter at the base and usually divided a foot or two above the ground into three or four stout 
upright stems four or five inches thick, and slender pendulous often much contorted branches forming 
a narrow round-topped symmetrical head. The bark of the trunk is an eighth of an inch thick and 
separates into loose hanging plate-like scales light gray and slightly tinged with red, from one to two 
feet in length and an inch or two in width, which, in separating, disclose the bright orange-colored inner 
bark. The branchlets are slender, and when they first appear are dark green and coated with hoary 
tomentum ; during their first summer they are dark red-brown, marked with minute pale lenticels, and 
covered with pale pubescence; in their first winter they are light cinnamon-brown, glabrous and 
lustrous, and, growing lighter colored during the summer and autumn, they become ashy gray the 
following year. The leaves are oval or obovate, acute or rounded at the apex, gradually narrowed 
and often unequal at the rounded wedge-shaped or rarely cordate base, and sharply or often doubly 
serrate with small triangular teeth ending in stout spreading callous tips; when they unfold they 
are covered with loose pale tomentum, which is thicker on the lower surface, and at maturity they 
are dark yellow-green and pilose above, pale and soft-pubescent below, from one to two inches long and 
from an inch to an inch and a half wide, with slender yellow midribs slightly raised on the upper side, 
and few slender primary veins connected by obscure reticulate veinlets, and occasionally forked near the 
margin; they are borne on slender nearly terete hairy petioles from a quarter of an inch to nearly half 
an inch in length, and turn a dull yellow in the autumn before falling. The stipules are oblong-obovate, 
pale yellow-green, and often tinged with red toward the apex, half an inch long, about an eighth of an 
inch wide, and caducous. The aments of staminate flowers appear in July, and at first are coated with 
thick hoary tomentum ; they are raised on stout peduncles clothed with rufous tomentum and sometimes 
nearly half an inch in length, or occasionally are sessile or nearly sessile, and during the winter are 
about half an inch long, with dark brown puberulous scales gradually contracted into long slender 
subulate points; they lengthen in May, and when fully grown are from an inch to an inch and a 
quarter in length, with broadly ovate concave scales rounded and abruptly narrowed at the apex into 
nearly triangular points, yellow-green near the base and bright red above the middle. The pistillate 
aments are about a quarter of an inch long, with ovate lanceolate light yellow-green puberulous scales 
ciliate on the margins. The strobile of fruit, which is fully grown by the first of July, is from an inch 
to an inch and a half in length, about three quarters of an inch in breadth, and hangs on a slender 
stem half an inch long and coated with long pale hairs; the involucres are furnished at the apex while 
young with conspicuous caducous tufts of pale tomentum, and are an inch long when fully grown, 
nearly glabrous at the apex, and sometimes slightly stained with red toward the base. The nut is about 
a quarter of an inch in length, and is gradually narrowed at the apex. 
Ostrya Knowlton, which is probably one of the rarest trees in the United States, has only been 
seen on the southern slope of the canon of the Colorado River in Arizona at a point seventy miles 
north of Flagstaff, where the post-office and camp of Tolfree have been established, and where it grows 
by the trail leading to the bottom of the cafion at elevations between six and seven thousand feet above 
