TREE FERNS OF NORTH AMERICA MAXON. 483 



latter with a huge thick trunk that is utterly disproportionate to the 

 crown of narrow, lanceolate, bipinnate fronds ; C. arborea, previously 

 mentioned and figured (pis. 2 and 3; pi. 10, fig. A) ; C. elegans (pi. 9, 

 figs. A and B) ; C. Tussacii, a Jamaican species with coarse, tripin- 

 nate fronds, everywhere shaggy with slender tawny or grayish scales; 

 C. nigrescens and C. araneosa, very much alike in their harsh, exceed- 

 ingly coriaceous, tripinnate blades and densely spiny trunks and 

 stipes; and C. portoricensis, a species with dark, lustrous, purplish- 

 brown vascular parts and large, nearly tripinnate blades. The last 

 species is apparently unique in having the outer surface of the 

 deeply cup shaped indusia rather densely clothed with simple yel- 

 lowish hairs. 



Only a few species of the section Eatoniopteris may be mentioned. 

 Perhaps the most interesting are C. Brunei and C. aureonitens, 

 already referred to in the preceding pages. The Costa Rican forms, 

 C. WerMeana, C. hemiotis and C. hastulata, constitute a natural group 

 in having the ultimate segments of the tripinnate fronds constricted 

 at the base, or even sessile. Three other species, C. Tuerckheimii, 

 C. gracilis, and C. divergens are unusual in having the larger pinnules 

 (divisions of the primary pinnae) mostly long-stalked. Cyaihea 

 insignis and C. princeps have the primary and secondary rachises 

 unarmed as to spines, but yet conspicuously rough from the presence 

 of the broken-off bases of the slender spiny-margined scales which 

 at first thickly invest them. At least one species, C. patellaris, has both 

 veins and leaf tissue glabrous, while its nearest ally, C. mexicana, 

 has the similar parts very minutely but distinctly glandular-setulose, 

 and in addition many of the veins simple, an unusual feature in this 

 genus. 



As to the characters which distinguish the species, it may again 

 be mentioned that although minute they are usually constant, if due 

 allowance be made always for minor variations which may be corre- 

 lated mostly with known differences of habitat, altitude, and geo- 

 graphic position; and that if a sufficient amount of well-prepared 

 material be brought together the recognition of the species will not 

 prove especially difficult. Indeed, the most surprising feature of all 

 is that species so similar in details of leaf form have been able to 

 develop such marked diversity in the general form, structure, and 

 disposition of minute scales and hairs and that these differences are 

 so nearly constant. An attempt has recently been made to give to 

 these structures some part of the weight in classification to which 

 they appear to be entitled. To this treatment * the reader is referred 

 for full descriptions of the North American species of this interesting 

 genus. 



* North American Flora, vol. 16, part 1, pp. 65-88, 1909. 



