THE LIMESTONE POLYPODY.
POLYPODIUM ROBERTIANUM.
P. fronds oroct, rigid, glandulosc, pentangular deltoid, subtornate ;
lower branches (or piimæ) hipinnato, stalked, their pinnulots or
lobulets oblong obtuse, crenate or nearly entire ; stipes glandulose.
[ria to X II.]
PoLYPOBTFM RoBEiiTiANUM, Jloffmann, Deutschl. FI. i i. i n a d d e n d a t o p . 10
(1 7 9 5 ) . Fries, Sum. Yeg. 8 2 . Koch, Synops. 2 e d . 9 7 4 . Nyman, Syll. FI.
Europ. 4 3 0 . Moore, Ilandh. Brit. Ferns, 3 e d . 66 ; Jd., 'Ferns of Gt. Brit,
and Ireland, Nature Printed, t . 6. Babington, Man. Brit. Bot. 4 e d . 4 2 0 .
Loive, Nat. IlisL Ferns, i. t . 28.
P oLY roD iUM CALCAiiEUM, Smith, FI. Brit. 1 1 1 7 (1 8 0 4 ) ; Id., Eng. Bot. x x i i .
t . 1 5 2 5 ; Id., Eng. FI. 2 e d . iv . 2 7 0 . Dealdn, Florigr. Brit. iy . 4 3 , fig . 1 5 8 2 .
Hooker <0 Arnott, Brit. FI. 7 e d . 5 8 2 . Nemman, Hist. Brit. Ferns, 2 ed.
1 3 1 . Sowerby, Ferns of Gt. Brit. 12 , t . 4. Willdenow, Sp. Plant, y . 2 1 0 .
Sprengel, Syst. Veg. iv . 6 0 . Presl, Tent. Pter. 1 8 0 .
PoLYPODiUM D i i y o p t e r i s , YAH., Bolton, Fil. Brit. 53 , t . 1. Bentham, Handb.
Brit. FI. 6 2 7 .
P o l y p o d i u m H i i y o p t e j i i s , /8. m in u s , De Candolle, FI. Franp. ii. 5 6 5 .
P o ly p o d i u m D i i y o p t e r i s , j8. K o b e i u t a n u m , liuprecht, Dist. Crypt. Vase. Ross.
52 . Ledebour, FI. Ross. iv . 5 0 9 .
P o ly p o d i u m D b y o p t e i u s , v . ca lc aP vEUM , Gray, Man. Bot. North. U. States, 5 9 0 .
N e p u b o d iu m D h y o p t e i u s , Michaux, FI. Bor. Amer. ii. 2 7 0 .
L a s t r e a c a l c a r e a , Bory, Diet. Class. d'Hist. Nat. ix . 2 3 3 . Newman, Nat.
Aim. 1 8 4 4 , 1 7 .
L a s t r e a R o b e r t i a n a , Newman, Hist. Brit. Ferns, 2 e d . 13.
P h e g o p t e r i s c a l c a r e a , Fée, Gen. Fil. 2 4 3 . J. Smith, Cat. Cult. Ferns, 17.
G y m n o c a r p i u m R o b e r t i a n u m , Neunnan, Phytol. iv . 3 7 1 ; Id., Appendix,
1 8 5 1 , x x iv . ; Id., Hist. Brit. Ferns, 3 e d . 6 3 .
Candex creeping extensively, branched, thicker than a straw,
dark-brown, scaly. Scales palo-brovTi, semitransparent, lanceolate.
Fibres dark-brown, branched, clothed with a brighter brown
pubcsoonoo.
Yeniation circinate ; the pinnules rolled up separately into little
globules, the pinnæ then rolled each separate inwards towards the
main raohis, which is next itself coiled up.
Stipes longer than tho frond, often twice as long, stoutish, succulent
when young, becoming stiff and erect, abundantly scaly about
the base, and witb a few scattered deciduous scales upwards
when young, minutely glandular, palo watory-gTCon, dulled by tbe
glaudulosity of tbe surface ; lateral to tho caudox, adherent, distinct.
Bachis glandulosc, tho part forming a stalk to tho lower
pinnæ much shorter and distinctly smaller than that between tho
first and second pairs of pinnæ.
Fronds six to eighteen inches in height, including tho stipes,
vdiich is usually more than half, sometimes two-thirds at least, of tho
loiigth : erect, of a firm herbaceous texture, deep dull grayish-grooii,
glandulose, elongately doltoid-pentaiigular, the pentagonal outline,
however, loss manifest than in P . Dryopteris, in consequence of the
less comparative length of the stalks of tho lower pinnæ. Tho
fronds aro not truly ternate, though tho larger size of the^ lower
pinnæ gives them a suhternate appearance; they are hipmnate,
with tho lowest pair of pinnæ snbbipiiinate or sometimes bipmnato
on the posterior side, which is tho most developed.
Finnæ variable, opposite boloiv, tho loiver largest pair somotinios
each six inches long, obliquely triangular, stalked, often bipinnate ;
tbe next pair stalked or sessile, pinnato-pimiatifid ; tbe upper ones
all sessile, pinnate or pinnatifid, becoming gradually less divided
towards tho apex. Pinnules of the loivor pair larger on the
posterior side, those of tho other pinnæ nearly equal ; those of each
succeeding pair rcsomhling the smaller ones of the pair next below
them. Pinnulets or lobulets oblong, obtuse, entire or oreiiatod.
Venation of tbo lower posterior pinnules consisting of a stout costa
or midvein, Avith a flexuose vein running up the centre of each
lobulet ; this is alternately branched, the venules oxtondmg to the
margin, simple, or very commonly forked, the vcnulo if simple, and
the anterior veinlet if divided, bearing a sorus near to tho margin.
Or, the vein extending up the lobulet may bo regarded as a midvein ;
its branches, sometimes simple and soriferous, as veins ; and the
branches of these, of Avhioh the anterior is mostly fertile, as venules.
Fructification on tho back of tho frond, scattered over its AA'hole
surface. Sori small, circular, consisting of numerous crowded
spore-oases, entirely Avithout indusia, arranged in a linoar submarginal
series along each side of the lobulets ; or about tbe sinus,
in a series between the midiib and margin, Avhcn tho lobules are
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