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2 i 6 F E R N S O F NORTH AM E R IC A .
large, dark-colored and quite globular. Mr. Faxon has observed
the three radiating vittæ which are found throughout
the genus.
Cheilanthes Lindheimeri differs from Ch. myriophylla in
having a very slender root-stock, and the covering of the frond
more decidedly tomentose, especially on the upper surface.
The pinnules, too, are smaller and more densely crowded.
C. Fendleri, which has also a slender root-stock, has no
tomentum, and the pinnules are not at all crowded.
Presl proposed a sub-genus of Cheilanthes for the species
with minute concave or vesiculiform pinnules, giving it the
name of Physapteris, and enumerating three species, C. len-
tigera, myriophylla and scariosa. Some years afterwards Fée
made a genus of the same group, calling it Myriopteris, and
dividing it into two sections, Fumyriopteris, for the species
with a proper involucre, and Cheilanthastrum, for those having
a recurved margin in place of an involucre. Fournier
keeps Fée’s genus Myriopteris, but says nothing about the
two sections. It is a very difficult group, for the species are
all much alike, and the earlier authors failed to indicate the
most distinctive points of difference.
Plate LX X IV ., Fig. 1 0 - 1 5 .— Cheilanthes Lindheimeri, from a
specimen collected by Liiidheimer himself. Fig. 1 1 is a secondary
pinna, enlarged, and having the scaly and tomentose covering mostly
removed. Fig. 12, a pinnule, almost denuded. Fig. 13 , a spore. Fig.
14. a scale from the lower surface. Fig. 15, entangled hairs from the
upper surface.
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