68 



at which the growing part extends itself and the obstacles to be 

 encountered in its removal ; but, once obtained, there is little risk 

 of loss, as it seems quite independent of difference of soil. 



The Common Brake was the Filix-fcemina, or Female Fern of 

 the old botanists, or those prior to the time of Linna3us, who trans- 

 ferred the title to another, the present Athyrium Filix-fcemina. 



There is reason to conclude that many exotic species, so con- 

 sidered, belonging to different parts of the world, may not be 

 really other than slightly varied forms of the Pteris aquilina, re- 

 sembling it closely as they do in habit, tendency to complexity in 

 the division of the frond, and other circumstances. Should future 

 observation render fact that which is at present merely speculative, 

 then might the fern before us rank as the most universally distri- 

 buted of all vegetable productions, extending its dominion 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 P. escu- 

 lenta. The rhizoma of our plant, like that of the latter, is edible ; 

 and though not employed in these islands as food, powdered and 

 mixed with a small quantity of barley-meal, it is made into a kind 

 of gruel called gofio, in use among the poorer inhabitants of the 

 Canary Islands, especially those of Palma and Gomera : its astrin- 

 gency, however, is so great, that it has been recommended for 

 dressing and preparing kid- and chamois-leather, and its qualities 

 as a vermifuge are said to equal those of Aspidium Filix-mas. The 

 large fronds form a durable thatch, and are used as litter for cattle : 

 in many parts of the country they are collected for fuel, especially 

 for heating ovens, and sometimes even for burning limestone. The 

 ashes contain a large proportion of alkali available in the manu- 

 facture of both soap and glass, and are often employed by country 

 people as a substitute for the former article, for which purpose they 

 are generally formed into balls by moistening and afterwards heat- 

 ing them in the fire ; in this state they are well known in some 

 districts in England by the name of ash-balls. A bed made of the 

 fresh-gathered fronds is a provincial remedy for the rickets. 



Genus 12. ALLOSOKUS. 



GEN. CHAR. Sori circular, near the extremities of the lateral 

 veins, confluent in maturity ; covered by the reflexed margin 

 of the pinnules of the contracted fertile frond fulfilling the 

 office of an indusium. 



Most recent botanists place this genus next to Potypodium, on 

 account of the form of the sori and the absence of a true indusium ; 

 but the eventually confluent fructification, forming an intromar- 



