Cyathea
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Taxonomy
This is by far the largest subdivision of the genus, and includes species with all formsof indusia and with none. I have not been able to distinguish sharply defined groups which could appear as main divisions of the key. The main key-characters are based on indusia, and allied species are sometimes separated by this method. The species with hemitelioid indusia are the most difficult to characterize clearly; this group is particularly polymorphic in Sumatra and in the Philippines. There may be hybrids, but the remarkably uniform characters of C. latebrosa (Wall.) Copel., a common species in Malaya of which I have seen a large number of specimens, indicates that quite small differences can be constant. Size of pinnules is not a reliable character, unless one can see ample material; plants growing in exposed conditions may have much smaller pinnules than others of the same species in the shade. However, the very large pinnules of C. incisoserrata Copel., otherwise very near C. latebrosa, appear to be constant, and are exactly reproduced in new plants raised from spores at Kew. For local floras it will probably be possible to devise keys based on macroscopic characters easily observed in the field; in preparing keys to cover all Malaysian species, I have not been able to use such characters.
I am not sure whether the hemitelioid species of tropical America should be placed in this section, or in a separate section; if the latter, the name Hemitelia is available for them (type-species H. multiflora (Sm.) R. Br.). Some exindusiate tropical American species appear distinct in their dermal appendages. These have been referred to Alsophila, but do not appear to be nearly related to the type-species of Alsophila, A. australis R. Br.; they need further study.
I am not sure whether the hemitelioid species of tropical America should be placed in this section, or in a separate section; if the latter, the name Hemitelia is available for them (type-species H. multiflora (Sm.) R. Br.). Some exindusiate tropical American species appear distinct in their dermal appendages. These have been referred to Alsophila, but do not appear to be nearly related to the type-species of Alsophila, A. australis R. Br.; they need further study.