478 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1911. 



thus obvious; for it is inconceivable that without this or some sirnilar 

 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 the large outer scales are of a silky texture, yellowish- 

 brown, up to 2\ inches long, in shape very narrowly lanceolate and 

 long pointed, borne 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 strikingly combined. 

 In shape 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, as in most other ferns. The margins of the scales 

 may be entire or irregularly lacerate, minutely saw toothed, or, as 

 already noted, even beset with stiff, bristlelike teeth. 



Of the North American members of the tribe Cyatheae 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 pinnas of Alsophila aspera, the plant mentioned by 

 Sloane. A peculiar, low-growing, bipinnatifid species, Cyathea Nockii, 

 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 

 borne similarly. Like the scales, they also in their structure and dispo- 



