624 FILICES. (ferns.) 
3* ALLOSORUS, Bernhardi. Allosorus. 
Fruit-dots roundish, without any proper indusium, borne on the 
ends of the simply forked veins, terminating free within the mem¬ 
branaceous margins, which are reflexed so as to cover them and 
form a sort of general involucre, soon confluent laterally so as to 
produce a broad and intramarginal transverse line of fructification, 
resembling that of Pteris. — Fronds 1 -3-pinnate, low, from slen¬ 
der creeping rootstocks ; the fertile usually more or less contracted. 
(Name from aXAor, various , and crcopos , a heap , for fruit-dot.) 
Presl. Smooth, low (3'-6' high) ; fronds thin, 
of few pinnae, which are pinnately parted into 3—5 oblong or linear- 
oblong, somewhat crenate divisions, or in the sterile frond ovate. 
(Pterisgracilis, Michx .) — Shaded rocks, Vermont to Michigan; rare. 
4. PTERIS, L. Brake, Bracken. 
Fruit-dots linear, confluent laterally in a line which borders the 
divisions of the frond, the continuous indusium fixed at the very 
margin, the inner edge free. Veins forked and free, bearing the 
sporangia at their apex. — Fronds 1- 3-pinnate or decompound, 
rather coriaceous. (The ancient Greek name of Ferns, from 
Trrepov, a icing , on account of the prevalent pinnate fronds.) 
§ 1. Pteris proper. — Indusium very narrow , at its attachment the 
veinjets connected at their very apex by a transverse receptacle which 
bears the sporangia. 
^ aquilina, L. (Common Brake.) Frond ternate at the 
summit of an erect stout stalk (l°-2° high), the widely spreading 
branches 2-pinnate ; pinnules oblong-lanceolate, the upper undivided, 
the lower more or less pinnatifid, with oblong obtuse lobes, margined 
all round with the indusium. —Thickets and stony hills, everywhere. 
Aug.—Whole frond 2°-3° wide, dull green. 
§ 2. Platyl6ma, J. Smith. — Indusium rather broad: sporangia oc¬ 
cupying a portion of the upper part of the closely approximated but 
unconnected veinhts, forming a broad continuous fruiting line. 
2. P. atropurpiirea, L. Stalk of the simply or somewhat 
doubly pinnate pale frond (6-9' high) dark purple and shining; 
pinnae, or their 3-7 divisions below, oblong or linear, entire, obliquely 
truncate or heart-shaped at the stalked base. — Limestone rocks; rare. 
I AUTEUI, L. Maidenhair. 
Fruit-dots roundish or crescent-shaped, occupying the edge of 
the lobes of the frond, the indusium appearing as a reflexed edge of 
