478 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1911. 
thus obvious; for it is inconceivable that without this or some similar 
protective feature individuals of such slow continuous growth could 
attain their great size and age. Tree ferns with trunks 20 to 80 feet 
high do not grow in a day. 
As offering diagnostic marks to assist in the recognition of the spe- 
cies also the scales are of the greatest interest, since however various 
their form, color, and structure these features are usually constant and 
distinctive for each species. The largest scales I have seen are those 
which densely clothe the 2-inch thick stipes of Cyathea Brunei. In 
this species et large outer scales are of a silky texture, yellowish- 
brown, up to 24 inches long, in shape very narrowly lanteolaté and 
long Sate hoiid in great profusion and widely spreading, and 
underlaid by successively smaller scales, the innermost of which are 
comparatively minute, slender, stiff, dark brown, and have minutely 
spiny margins. Very few species show so great variation in this par- 
ticular. The prevailing color of the scales is some shade of brown, 
ranging in different species from yellowish or reddish-brown to chest- 
nut-colored, or purplish-brown; a few are white, others almost coal 
black; and in certain species two colors are Seanad combined. 
In woe: there is nearly every variation between the rounded-ovate 
and slender almost needlelike form, and in texture from delicately 
membranous to very thick. As a rule, the thickest scales are the 
most highly colored, asin most other ferns. The margins of the scales 
may be entire or ce lacerate, minutely saw toothed, oT, as 
already noted, even beset with stiff, bristlelike teeth. 
Of the North American meee of the tribe Cyathee a few are 
bipinnatifid, though most are either very deeply tripinnatifid or 
tripinnate, and a very few quadripinnate or nearly so; none are 
simple. In outline their blades range from lanceolate to broadly 
ovate. An example of the tripinnatifid type is shown in plate 7, 
representing pinne of Alsophila aspera, the plant mentioned by 
Sloane. A peculiar, low-growing, bipinnatifid species, Cyathea Nocku, 
of Jamaica, is figured at about two-fifths natural size in plate 8. 
Upon the rachises and midveins of most species, and also upon the 
ultimate veinlets and upon the leaf tissue of many of these, occur 
various small, even minute, scales of varied form and color. They 
may be flattish or convex, thick or exceedingly thin and delicate, 
roundish, linear, deeply cleft, fringed, or either'reduced to the form 
of minute stellate bristles; but whatever their character and position 
upon the several parts of the blade they will be found, within certain 
limits, to be very constant and, like the spines and scales of the stipe, 
to serve as definite recognition marks for the species. Hairs, some 
composed of several cells, others unicellular and glandlike, are also 
bornesimilarly. Like the scales, they also in their structure and dispo- 
