484 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1911. 



THE GENUS HEMITELIA. 



In the section Eucyathea of the genus Cyathea the indusium has 

 been shown to be inferior in attachment and to partially envelop 

 the base of the sorus upon all sides within its cup-like walls. The 

 indusium of Hemitelia is not unlike an indusium of this sort cut 

 vertically in half; that is, it is deeply concave or hood-shaped when 

 young, and from its point of attachment at the base of the receptacle 

 bulges outward, surrounding the sporangia of at least one-half of the 

 sorus upon one side. When the sporangia expand at maturity the 

 indusium is borne back against the leaf surface and forced to assume 

 a flattish, semicircular form. In so doing it usually splits part way 

 to the base into several irregular spreading lobes. These are com- 

 monly short and rounded, two to four in number, and slightly con- 

 cave; but in a very few species (for example, Hemitelia muricata of 

 the Lesser Antilles) the indusium becomes sharply cleft into several 

 elongated, acute segments, which stand out obliquely from the leaf 

 surface, mixed among the sporangia, and are not very readily 

 observed, more especially since they are deciduous. Nearly all 

 species of the genus, however, have indusia of the former sort; and 

 this without regard to differences of leaf form. The receptacles are 

 similar to those of Cyathea. 



Hemitelia is generally accepted at present as consisting of two 

 sections, Euhemitelia and Cnemidaria, distinguished by differences 

 in habit, leaf cutting, and venation. The first section, typified by 

 Hemitelia multiflora, embraces mainly plants with upright trunks 

 and large tripinnatifid fronds, similar in form to those of most species 

 of Cyathea, the segments or ultimate divisions being relatively 

 small. Also in free venation, scales, and minute characters other 

 than those of the indusia, the half dozen or more North American 

 species of Euhemitelia are precisely like those of Cyathea. The 

 usual form of the indusia is shown in plate 10, figure B, representing 

 H. multiflora. 



Of far greater interest is the section Cnemidaria, composed of 

 plants which are rarely arborescent and whose leafy fronds are of 

 very simple form. The typical and best known species of this group 

 is Hemitelia horrida, which is nearly confined to the Greater Antilles. 

 An unusually well-developed plant of this is shown in plate 11, 

 affording an excellent idea of the broad and relatively large divisions 

 of the deeply bipinnatifid, nearly bipinnate fronds. Other species 

 have smaller and simply pinnate leaves, with the margins of the 

 pinnae entire, undulate, crenate, or marked by regular rounded or 

 angular lobes; and a few are even larger than H. horrida, with tho 

 margins similarly variable in form. In some species the lobes are 

 sharply acute; in others regularly rounded. There are marked dif- 



