MAXON—-STUDIES OF TROPICAL AMERICAN FERNS. 415 
than halfway around the base of the receptacle and nearly forming 
a shallow cup, thus approaching the form which distinguishes several 
of the species of Cyathea, section Eucyathea. The transition from a 
delicate, fragile, deeply splitting indusium like that of Hemitelia 
muricata to the mere vestigial scale observed in the Jamaican Alsophila 
parvula and the Australasian Alsophila australis (which is the type 
species of Alsophila), and further to the complete absence of even a 
vestigial scale, is not a very great step, and there are several species 
whose ready reference to one genus or the other requires good material. 
Whether there is warrant for giving so much weight to indusium 
characters in the distinction of the genera is open to question. The 
writer, as heretofore explained, has preferred to follow the usual 
practice. In any case these characters are fairly constant for the 
species and upon careful examination are very useful in distinguishing 
them. 
KEY TO THE SPECIES. 
Lamina bipinnate, the pinnules serrate-crenate to barely pinnat- 
ifid. 
Pinne 20 to 24 cm. long; pinnules deeply serrate-crenate.... 1. H. elliottt. 
Pinnz 40 to 60 cm. long; pinnules mostly pinnatifid about 
halfway to the ¢ sta. 
Indusia brown, dimidiate, deeply lacerate-fimbriate, the 
divisions slender, fragile, fugacious............... 2. H. sessilifolia. 
Indusia much larger, whitish, saccate or subeyathiform, 
subentire or shallowly lobed, persistent. ......... 3. H. wilsoni, 
Lamina very deeply tripmnatifid. 
Sori inframedial, often borne close to the costa. 
Segments 12 to 14 pairs, distant, the sinuses obtuse...... 4. H. sherringii. 
Segments 20 to 23 pairs, approximate, the sinuses sharply 
acute. 
Indusia conspicuous, bullate, erose or shallowly cleft. 5. H. calolepis. 
Indusia obscure, deeply cleft, the divisions lacerate 
to filamentous.........-.-.---.------------- 6. H. costaricensis. 
Sori medial or distinctly supramedial. 
Larger pinnules about 13 pairs per pinna................ 7. I. escuquensis. 
Larger pinnules 18 to 25 pairs per pinna. 
Indusia small, shallowly lobed, persistent. . ...... 8. H. multiflora. 
Indusia large, very deeply cleft into seve veral long 
slender segments, these fugacious............. 9. H. muricata, 
1. Hemitelia elliottii (Baker) Underw. MS. 
Alsophila elliottti Baker, Annals of Botany 6: 96. 1892. 
Caudex said to be very short; fronds 90 to 120 cm. long; stipe 30 cm. Jong, armed 
with spreading sharp spines, divested of scales with age; lamina subdeltoid, 60 to 
90 cm. long, bipinnate, the primary rachis mottled reddish brown, slightly rough, 
glabrescent; pinnz narrowly oblong-lanceolate, 20 to 24 cm. long, 5 to 6 em. broad, 
subsessile, long-acuminate, the secondary rachis stout, reddish, distantly muricate, 
glabrescent, very delicately and inconspicuously foliaceo-marginate except at the 
base; pinnules about 20 pairs, linear-oblong, 2.5 to 3 em. long, 7 to 9 mm. broad, 
deeply serrate-crenate, approximate to subdistant, sessile, or those toward the apex 
semiadnate. the apical ones fully adnate and decurrent; costules stout, elevated, 
2797°.— 14-3 
