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13 0 F E R N S OF NO R TH AM E R IC A .
& B a k e r , Syn. Fil., p. 301. — F o u r n i e r , Pl. Mex., Crypt., p.
130. — G a r b e r , in Bot. Gazette, iii., p. 84.
Polypoditcm exaltatuzn, L in n æ u s , Sp. Pl., p. 1548.
A sp id ium exaltatum, S w a r t z , Syn. Fil., p. 45. — S c h k u i i r , Krypt.
Gew., p. 3 3 , t . 32 é .— W i l l d e n o w , Sp. Pl., v . , p. 229.— R a d d i ,
Fil. Bras., p. 30, t . 46.
Nephrodium exaltatum, L in k , Fil. Hort. Berol., p. 109.
Many nominal species of N eph rolepis are referred to N . exaltata
in Spe cies F ilic um , among them N . hirsutula, P r e s l , -a form with
hirsute-pubescent pinnæ.
H a b . — On decomposing vegetable matter and on the trunks of
trees, particularly the Cabbage Palmetto. South Florida, Dr. C o o p e r ,
Dr. P a l m e r , W. R . T o m p k in s , Dr. G .a r b e r , Capt. J. D o n n e l l S m i t h ,
Miss R e y n o l d s , etc., etc. It is found in Mexico, the West Indies,
Central and South America, Southern Asia, China, the Pacific Islands
Australia, and parts of Africa. The hirsute form is more common in
India, China and Polynesia, but is found also in several parts of Tropical
America.
D e s c r i p t i o n : — The genus Nephrolepis was proposed, in
1S34» by bl. W. Schott for those species of Nephrodium or
Aspidium which had a reniform indusium obliquely affixed
by its emarginate base to the side of the enlarged tip of the
fertile vein. He gives excellent analytical drawings of N.
exaltata, and mentions “N. pectinata, biserrata, etc.,” as also
examples of his genus. In the Tentamen Pteridographice, of
Presl, two years later, the genus is admitted an d. over a
score of species referred to it. A new distinctive character
F E R N S OF NORTH AM E R IC A . 131
is also indicated: — “ Pinnæ truly articulated to the rachis,
and easily separating from it.” Fée divided the species into
two genera, Nephrolepis and Lepidocaulon, assigning to the
former the species with a broadly reniform indusium somewhat
laterally attached to the receptacle, and to the latter
those with a round-reniform indusium, affixed by the centre;
but since specimens are very common in which both forms
of indusium occur on the same pinna, it is clearly impossible
to make the special form of the indusium a generic character.
A peculiarity in the genus, which escaped the observation
of many of the earlier pteridologists, is the indefinite
growth of the frond. According to the observations of Mettenius,
there is no necessary limit to the apical development
of the frond in mature plants. What he has to say on the
subject is translated below.'
' “ The rhizoma o f all the cultivated species is raised erect from the soil, without
reaching any great height, and is covei'ed with the gradually decaying leaf-stalks.
In all the cultivated species, just below the points where the fronds are inserted on
the rhizoma, there originate filiform runners, which either produce buds somewhere on
their course above-ground, or develop tubers at the end which enters the soil, and thus
contribute to the multiplication o f the plant. The fronds are characterized by the perennial
indefinite growth o f the leaf-stalk [rachis], and the consequent unlimited periodical
production o f pinnæ at the uninjured circinate apex, long after the older pinnæ have fruited
or fallen off. Only in the earliest fronds o f plants grown from spores (and also in
N . platyotis and N . davallioides, after the formation o f fertile pinnæ) does the development
o f the frond terminate with a gradual diminution o f the size o f the pinnæ, whilst
the highest rudimentary side-pinna blends with the proper terminal segment. In N .
exaltata the oldest fronds continue to develop at the apex, and the growth o f the frond is
limited only by some injury happening to the apex. The limit o f the yearly increase o f
the frond is always indicated by the smaller size o f the segments.” \^Fil. Hort. L ip s ., p. 99.]
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