STUDIES OF TROPICAL AMERICAN FERNS—NO. 5. 
By Witu1am R. Maxon. 
INTRODUCTION. 
The following paper, like earlier ones published’ under the same 
collective title, relates mainly to lesser groups of tropical American 
ferns which have been either neglected or very generally misunder- 
stood. Examples of the latter sort are found in Hemitelia (section 
Euhemitelia) and the group of Polypodium duale; and of the former 
in the American representatives of the genus Oleandra. The last 
mentioned fall under several readily recognized species, marked by 
excellent characters, and their classification was made comparatively 
easy by the presence of sufficient material and a definite knowledge 
of the few species previously described. The study of Euhemitelia 
and of the Polypodium duale group, however, offered the usual diffi- 
culties connected with an examination of scattered type specimens. 
The case of Polypodium myosuroides, a species of the last group, 
affords indeed an excellent illustration of the value of type speci- 
mens, since it involves the mistaken application of this name for 
exactly 100 years. As explained below, the name Polypodium 
myosuroides was given by Swartz in 1788 to certain Jamaican speci- 
mens of which it is peculiarly descriptive. In 1804 Schkuhr figured 
mistakenly, as an example of myosuroides, a second Jamaican species. 
Later authors, including Willdenow and Swartz himself, accepted 
Schkuhr’s plate as illustrating P. myosuroides, although it represents 
a very distinct species latterly distinguished by Jenman (under the 
wrong name) and renamed P. delitescens by the writer in 1905. The 
confusion of the two by Swartz and Willdenow is partially explained 
by the preservation of a small detached frond of P. delitescens among 
the tufts of P. myosuroides in the Swartz herbarium at present and 
by the fact that both species are represented in the fragments sent 
by Swartz to Willdenow. 
In the writer’s opinion fern study is not seriously hampered by 
that lack of appreciation of the value of types which is evident 
among workers in some other groups. The confusion in the case just 
cited arose partly from a paucity of material, and a consequent failure 
1 Contr. U. S. Nat. Herb. 10: 473-508. pls. 55, 56. March 30, 1908. Ibid. 13: 1-43. 
pls. 1-9. June 30, 1909. Ibid. 16: 25-62. pis. 18-34. June 19, 1912. Ibid. 17: 133-177. 
pls. 1-10. June 20, 1913. 
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