46 FERNS OF THE LAKE COUNTRY 



the lower pinnae three to four inches long, ovate- 

 acuminate, the central six inches long, linear oblong 

 acuminate, all ascending, opposite or sub-opposite and 

 distant below ; pinnules (basal ones of second pair of 

 pinnse) an inch and a quarter long, shortly petiolate, 

 pyramidal or pyramidal ovate, acute, pinnatifid, almost 

 pinnate ; lobes oblong, about three-quarters of an inch 

 long, obtuse, the lowest sub-lobate at the base, other- 

 wise serrated, the serratures most numerous and pro- 

 minent at the apex, acute, mucronulate. The pinnules 

 become gradually less pyramidal or ovate, and more 

 oblong, at length linear oblong, as they recede from 

 the main rachis ; below, except the lowest, they are 

 also sessile, narrowly attached, but gradually more and 

 more adnate upwards. The pinnules of the upper 

 pinnse resemble the smaller pinnules of the lower. 



The venation consists in the larger lobes of a flexuous 

 primary midvein from which alternate venules proceed 

 toward the serratures, sometimes branched, the sori 

 being situated midway on the simple venules and close 

 above the fork upon the branched. In the smaller 

 pinnules the vein bears a sorus midway on its lowest 

 anterior venule, so that a row of sori is formed on each 

 side of, and at a little distance from, the principal vein. 

 The basal lobes often bear two or three other sori, and 

 are traversed by a series of alternate simple venules. 



The fructification occupies the whole back of the 

 frond, from base to apex. The sori are prominent and 

 distinct, in two series, near the vein of the smaller 

 pinnules and on the lobes of the larger. Indusium 

 persistent, reniform, indistinctly erose-dentate (irregu- 



