ROBINSON: PTERIDOPHYTA OF THE HAWAIIAN ISLANDS 4597 
thicket, suggest the appearance of blackberry vines by the road- 
side. 
The type was collected upon the U. S. Exploring Expedition of 
1854. 
DRYOPTERIS ACUTIDENS C. Chr. Ind. Fil. 250. 1906 
Phegopteris spinulosa Hilleb. Fl. Haw. Is. 566. 1888. Not 
Dryopteris spinulosa (Miill.) Kuntze. 
Polypodium spinulosum Baker, Ann. Bot. 5: 459. 1801. 
TYPE LOCALITY: Southern slope of Haleakala, Maui. 
DisTriBuTION: Along banks of streams, at elevations of 400- 
1,400 m., Hawaiian Islands. 
SPECIMENS EXAMINED: Hawaii, Hillebrand B, C; Oahu, Robin- 
son 177 V; Maui, Hillebrand B, C; Robinson 384 V; 604 V; 614 V; 
Kauai, Heller 2874 C; Hawaiian Islands, Baldwin 76 C; Hillebrand 
B; Lydgate B. 
There is a marked superficial resemblance between D. acutidens 
C. Chr. and the North American D. dilatata (Hoffm.) A. Gray, 
but there is no trace of an indusial covering for the sorus in the 
youngest specimens of D. acutidens. 
DRYOPTERIS UNIDENTATA (Hook. & Arn.) C. Chr. Ind. Fil. 299. 
1905 
Polypodium unidentatum Hook. & Arn. Bot. Beech. 105. 1832. 
Phegopteris unidentata J. Sm. Ferns Brit. & For. 170. 1866. 
Nephrodium unidentatum Diels in E. & P. Nat. Pfl. 14: 174. 1899. 
TYPE LOcALITY: Hawaiian Islands. 
DIsTRIBUTION: In forests at 600—1,200 m. elevation, Hawaiian 
Islands. 
SPECIMENS EXAMINED: Hawaii, Hillebrand B; Maui, Hille- 
brand B, C; Molokai, Hillebrand B, C; Oahu, Robinson 104 V; 
Kauai, Hillebrand B, C; Hawaiian Islands, Baldwin 79 B, C; 
Gaudichaud B; Hillebrand B; Baldwin V. 
Hillebrand’s variety paleacea of this fern is apparently a form 
that has arisen from ecological causes rather than a stable 
variation; thus the tall habit and light color are characteristic 
of the plants growing in the deep forest at higher elevations than 
that of the dark green plants with short caudex. 
