UnpDERWoopD: AMERICAN FERNS 251 
species, which has a relatively large range, is distinct from either 
the Japanese or Malayan species, and has already been twice 
named. 
With this general account of the genus and its sections we 
present a preliminary synopsis of the North American species : 
Primary branches bipinnate. (2 mesa ‘ygium Diels. ) 
Pinnules contiguous, mostly altern 1. D. Bancroftii. 
Pinnules distant, mostly (? ) aged 3. D. Brunei, 
gut “one simply p (sometimes repeatedly) 
Ing. 
eS all naked up to the final pair of pectinate pinnae. 
With a pair of reflexed pinnae at each fork. (3 Heterop- 
terygium Diels. ) 7. D, flexuosa. 
Without reflexed pinnae at the forks. (2 Acropterygium 
Diels. ) 
Ultimate pinnae sessile. 15. D. pectinata. 
Ultimate pinnae stalked (7, ¢., the rachises naked 
at the base) 
Rachises zigzag, with reflexed segments. 17. D retrofiexa. 
x Rachises i. with horizontal segments. 16. D. fpteridella. 
Branches (some or all) pectinate; pinnae pinnatifid to the 
: base. (4 Baines ee Diels. 
: Once forked, the forks of the second and successive 
orders appearing like a bipinnatifid leaf; sinuses 
| between the teeth broad. 13. D. orthoclada. 
) Twice to four times forked. 
Primary internode (7. ¢., stem between Ist and 
fork) naked 
Under surface more or less tomentose. 5. D. cubensis. 
Under ee smooth or at most ope pubes- 
nt; rachises mostly sc 
Pinus narrow epi . cm. wide) ; 
mostly ed. 
Scales ot Withey buds dark-ful- 
vous ; segments granular-glaucous Ce 
beneath. 4. D. costaricensis. 
Scales of axillary buds pale-brown ; 
segments faintly pubescent beneath, one 
not glaucous. 11. D. jamaicensis. 
Pinnae wider (3.5-5 cm.). 
Under surfaces glaucescent; rachises 
densely-covered with pale spread- 
ing scales. 
Under surfaces faintly pubescent; 
hi 
2. D. bicolor. 
ulvous; scales of ultimate 
rachises with dark centers. 12. D. mellifera. 
