INTRODUCTION TO CRYPTOGAMIC BOTANY. 519 



with that of its antipodes, New Zealand, we find several 

 common to both ; which is the more remarkable from these 

 two localities being the richest in species in their respective 

 latitudes. Again, the ferns of Tasmania are, with few excep- 

 tions, identical with those of New Zealand ; and lastly, the 

 occurrence of the rather common Australian and New Zealand 

 Gymnogramma rutcefolia in the Pyrenees (where it is ex- 

 tremely scarce), and nowhere else in the whole world, so far 

 as is kuo-vvn, is one of the most remarkable facts in the dis- 

 tribution of plants that has ever been made known. Amongst 

 a few anomalies in the diffusion of the order are the dis- 

 similarity of the Ferns of St. Helena and Ascension, a fact 

 which admits of no known explanation, and the presence of 

 the tropical Trichomanes speciosutn in South Western Ireland, 

 Avhich may, however, be readily accounted for by the humidity 

 of that locality and its geograj^hical position. 



586. " The genera of ferns are founded on such arbitrary 

 characters, that it is imjDOssible to draw any conclusions from 

 their distribution ; the majority, however, of the temperate 

 genera are foimd in all temperate and tropical latitudes, and 

 the tropical genera are for the most part common to both the 

 Old and the New World. Loniaria and Gleichenia are 

 almost the only well-marked genera common in south tempe- 

 rate regions, which are not found in the northern." 



587. The uses of ferns are more numerous than those of 

 mosses, though they are not very important. They doubt- 

 less help to form soil with other cryptogams, but their pro- 

 perty is rather to take possession altogether, than to aid in 

 the production of other plants. Several of them, when burnt, 

 produce ashes, useful for manure, or, as crude matter, for the 

 chemists. The long creeping rhizoma of a variety of Ptcrls 

 aquilina was formerly much used in New Zealand for food. 

 It abounds in starch and mucilage ; but if the New Zealand . 

 variety is not more palatable than our own, it is a very 

 undesirable food.* The large rhizoma of Maratt'ia sallcina 



* The rliizoma of our own form of P. aquilina when roasted lias 

 just the slimy consistence, taste, and odour of ill-ripened Brinjals when 

 cooked, than which nothing can be a worse compliment. The great 



