TREE PERNS OF NORTH AMERTCA MAXON. 460 



species; for example, Hemitelia Smithii with Cyathea medullaris and 

 C. dealbata. 



DIMENSIONS AND SHAPE OF TRUNK. 



The stem or trunk in the Cyatheacese 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 AlsopMla excelsa, 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. MacArihuri, 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 AlsopMla armata, which Jenman records 

 as sometimes reaching 50 feet in Jamaica, "the head gradually 

 diminishing in size as the stem lengthens." 



The smallest member of the family in the world is AlsopMla 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 \\ inches broad. The smallest of the 

 North American species is the Jamaican Cyathea Nockvi (pi. 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 3^ 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 

 Cyatltea minor of eastern Cuba, whose trunk measures only 1 to 1^ 

 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 



