TREE FERNS OF NORTH AMERICA—-MAXON. 469 
species; for example, Hemitelia Smithii with Cyathea medullaris and 
C. dealbata. 
DIMENSIONS AND SHAPE OF TRUNK. 
The stem or trunk in the Cyatheacee varies greatly in dimensions, 
shape, and direction, and in most characters of outward appearance 
and covering, though for a given species these features are, with a 
few exceptions, fairly constant in mature individuals. The tallest 
tree fern known is Alsophila eacelsa, a nearly extinct species occurring 
upon Norfolk Island, to the east of Australia, whose trunk John 
Smith has stated to measure from 60 to 80 feet in length. Scarcely 
inferior to this is A. MacArthuri, found upon Lord Howe’s Island, 
which, according to Maiden, attains a height of from 60 to 70 feet. 
Among American species the nearest approach to these dimensions of 
length is found, perhaps, in Alsophila armata, which Jenman records 
as sometimes eine 50 feet in Jamaica, ‘‘the head gradually 
diminishing in size as the stem lengthens.”’ 
The smallest member of the family in the world is Alsophila Kuhnii, 
recently described from the Cordillera of Colombia, in which the short 
rootstock is erect and the leaves (including the leaf stalks) but 8 
inches long, the blade less than 14 inches broad. The smallest of the 
North American species is the Jamaican Cyathea Nockii (pl. 8), looking 
most like some coarse bipinnate wood fern (Dryopteris or Poly- 
stichum), its relatively stoutish stem 4 to 8 inches long, prostrate 
upon the ground and rooting underneath, its fronds 1 to 34 feet long, 
borne in a crown. 
Certain species show, likewise, a slenderness of stem which is aston- 
ishing in relation to the enormous spread of crown, while others have 
remarkably thick trunks which are of very different internal struc- 
ture. The slenderest North American tree fern known to me is 
Cyathea minor of eastern Cuba, whose trunk measures only 1 to 14 
inches in diameter, though rising to a height of 6 to 12 feet. A 
Ceylon species, Cyathea sinuata, with curious narrow, nearly entire 
strap-shaped leaves, is even more slender. 
Exact data upon the thickness of tree fern trunks are not very 
-abundant. Darwin, in the Voyage of the Beagle, mentions a trunk 
(the genus and species not stated) in Van Diemen’s Land which had 
a circumference of 6 feet, nearly 2 feet in diameter. Mr. H. W. 
Henshaw, of the United States Department of Agriculture, measured 
trunks of Cibotium (supposed to be C. Menziezii) in the district of 
Olaa, Hawaii, many of which (including the dense covering of adven- 
titious roots) were 3 feet in diameter, and a single one 4 feet. These 
are said to have grown usually as undergrowth in the forest, but also 
in partial clearings, where they attain a height of 40 feet, large 
