358 A DIANTE&. PART n. 



upper and under epidermis, from which they are in- 

 dividually extensions. This fern is so universal in 

 Britain, as to exclude in some places almost every other 

 kind of vegetation, and is so well known, that it may 

 appear superfluous to mention that the fronds are 

 deltoid, with an elongated, stem-like petiole two or 

 three times divided, the primary pinnse opposite, the 

 ultimate segments oblong, obtuse, and confluent. There 

 are exotic forms of Pteris in every part of the world, 

 which are mere varieties of the Pteris aquilina, so that 

 the Bracken may be said to rank as the most universally 

 distributed of all vegetable productions, extending from 

 West to East, over both continents and islands, in a 

 zone reaching from Northern Europe and Siberia to 

 New Zealand, where it is represented by, and perhaps 

 identical with, the well known Pteris esculenta. 



The Allosorus crispus, Parsley fern, or Curled Rock 

 Bracken, which may be taken as a type of its genus, is 

 by some authors referred to the same group of Pteridese, 

 though others regard it as one of the Polypodiese. 

 It is a pretty little fern, growing in tufts in sheltered 

 crevices of mountain rocks, from Lapland to the Medi- 

 terranean. The fronds are deltoid, twice or three times 

 pinnate, and of two kinds. The ultimate divisions of the 

 barren fronds are wedge-shaped, cut, and toothed ; those 

 of the fertile fronds are linear, oblong, and entire. 

 Although the sori are at first circular, and situated near 

 the extremities of the lateral veins, they become confluent 

 in maturity, and being covered by the reflexed margin 

 of the pinnules of the contracted but scarcely altered 

 fertile frond, instead of by an indusium, they bear some 

 resemblance in fructification to Pteris aquilina. 



The Adiantiese form an exceedingly numerous and 

 mostly tropical group of ferns, in which the rhizome is 

 creeping or globose. Their sori are linear or oblong, 

 straight or curved, and growing on the under- side of the 



