SECT. vm. FILICES. 335 



SECTION YIIL 



FILICES, OE FEENS. 



OP all the spore-bearing families, the Ferns are the 

 most universally known. They may easily be recognized 

 by the coiling inwards of their young leaves in spring 

 previous to expansion, and by the arrangement of the 

 fruit on their undersides when expanded. The Ferns 

 are exceedingly numerous both in genera and species, 

 and vary from low herbaceous plants of an inch high, 

 to trees with upright trunks forty or fifty feet or more 

 in height, bearing a graceful coronet of leaves at their 

 extremity. The tree ferns come to the utmost perfec- 

 tion in the warm, moist islands of the tropical oceans. 

 Their boreal limit is about the thirty-seventh parallel 

 of north latitude, but, on account of the vast extent of 

 ocean in the southern hemisphere, they reach the for- 

 tieth or fiftieth parallel of south latitude, the more 

 copious evaporation , and the consequently moisfcer air 

 and soil, being specially congenial to the fern tribe. 

 For that reason a most luxuriant fern vegetation prevails 

 in Juan Fernandez, Western Chili, and New Zealand. 

 In the latter there are one hundred and twenty species, 

 some of which are subarborescent, while others form 

 tree ferns of considerable altitude.. Shade is not abso- 

 lutely requisite to ferns, for many of them grow luxuri- 

 antly when exposed to the sun, provided the soil be damp. 

 The range of the non- arborescent ferns is very ex- 

 tensive. According to Dr. J. D. Hooker, twenty-one 

 species have been found in Fuegia and the Falkland 



