THE BRAKES, OR BRACKEN. 
Gunus XI: PTERIS, Linneus. 
Gen. CHar.—Sori indusiate, marginal, linear, continuous or 
interrupted; the receptacles linear transverse uniting the apices of 
the veins in the fertile fronds. Indusium of the same form, mem- 
branaceous [double in P. aquilina]. Veins simple or forked from a 
central costa; venules free. 
Fronds varying from pedate to decompound, often of large size, 
herbaceous or coriaceous. 
Caudex short erect, or creeping, sometimes much elongated and 
subterraneous. 
This extensive and varied group is known among the linear- 
fruited indusiate genera by having its sori marginal, and at the same 
time removed from the costa. In Lomaria, which has already been 
mentioned in contrast to Blechnum, the marginal sori are coincidently 
costal in consequence of the contraction of the fronds; but in Péeris 
where they are also quite marginal, the fronds are not much if at 
all contracted, so that they appear distant from the costa. In other 
technical characters, e. g., in their free veins, and strictly marginal 
indusia, these genera have a close resemblance, though they are in 
reality sufficiently and readily distinguishable from each other. 
The genus Pieris has been divided into two sectional groups. Of 
these, $ Eupteris, containing the well-known garden P. longifolia and 
P. crenata, and embracing the majority of the species, is known by 
having its vernation terminal, that is the young fronds are always 
developed from the extremity or apex of the caudex. The $ Or- 
nithopteris has the vernation lateral: in other words, the young 
fronds spring up from a point behind the apex or growing point of 
the caudex, or at least the caudex elongates so rapidly that the 
fronds become outstripped in their development; this latter group is 
represented by the common P. aquilina and its allies. 
This Ornithopteris section of the genus appears to be also marked 
by another peculiarity, namely by the presence of a second or inner 
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