FERNS. 34'7 



Equisetacea3 accompanies their geographical approximation 

 to the Equator, is found in the fossil species of this order to 

 accompany the higher degrees of Antiquity of the strata in 

 which they occur; and this without respect to the latitude, 

 in which these formations may be placed. M. Ad. Brong- 

 niart (Prodrome, p. 167) enumerates twelve species of 

 Calamites and two of Equiseta in his list of plants found in 

 strata of the carboniferous order. 



Ferns.* 



The family of Ferns, both in the living and fossil Flora, 

 is the most numerous of vascular Cryptogamous plants.f 

 Our knowledge of the geographical distribution of existing 

 Ferns, as connected with Temperature, enables us in some 

 degree to appreciate the information to be derived from the 

 character of fossil Ferns, in regard to the early conditions 

 and Climate of our globe. 



The total known number of existing species of Ferns is 

 about 1500. These admit of a threefold geographical dis- 

 tribution : 



1. Those of the temperate and frigid zone of the northern 

 hemisphere, containing 144 species. 



2. Those of the southern temperate zone, including the 

 Cape of Good Hope, parts of South America, and the extra* 

 tropical part of New Holland, and New Zealand, 140 

 species. 



* See PL I. No. 6. 7. 8. 37. 38. 39. 



\ Ferns are distinguished from all other vegetables by the peculiar divi- 

 sion and distribution of the veins of the leaves; and in arborescent species, 

 by tlieir cylindrical stems without branches, and by the regular disposition 

 and shape of the scars left upon the stem, at the jioint from which the 

 Petioles, or leafstalks, have fallen off. Upon the former of these characters 

 M. Ad. Brongniart has chiefly founded his classification of fossil Ferns, it 

 being impossible to apply to them the system adopted in the arrangement of 

 living Genera, founded on the varied disposition of the fructification, which 

 IS rarely preserved in a fossil state. 



