FILICES. 1031 



XC. THE FERN FAMILY. FILICES. 



Herbs, with a perennial, short, or tufted, or creeping rootstock 

 (in some exotic species growing up into a tall, woody stem), or 

 rarely annual ; with radical or alternate leaves, which, as they also 

 partake of the nature of branches, are distinguished by the name 

 of fronds. In most genera these fronds are, when young, rolled 

 inwards at the top, and the rootstock, and sometimes also the 

 stalks of the fronds, are more or less covered with brown, scarious, 

 usually pointed scales. Fructification consisting of capsules, 

 called spore-cases {sporangia), sometimes small and almost dust- 

 like, arranged either in clusters, called sori, on the under surface 

 of the frond, and often covered when young, with a thin membrane, 

 called the indusium, or in little involucres on the margin of the 

 frond ; sometimes rather larger, in spikes or panicles at the top of 

 the frond, which has, lower down, either leafy branches or one 

 leaf. These capsules open in various ways to discharge the minute, 

 usually microscopical spores. 



A very large Order, abundantly diffused over the whole surface of 

 the globe, especially in moist climates, although some species may be 

 found in the chinks of the hottest rocks. The elegance of their foliage 

 has of late years attracted as much interest in them on the part of cul- 

 tivators and amateurs, as has their fructification and germination on 

 the part of the physiologist. It has long been known that they can be 

 reproduced from their spores, but it has only lately been ascertained 

 that these spores when sown are developed into minute, green, leafy 

 expansions, called prothalli, which alone have any analogy to the 

 flowers of other plants. For on the prothallus are produced, minute 

 bodies, which have been compared to stamens and pistils, from whence 

 the young Fern is subsequently developed. The spore may, under 

 this theory, be said to be a young flower-bud, which only opens after it 

 has fallen, the spore-case being an involucre enclosing innumerable 

 buds, and the sorus a whole inflorescence. 



The limitation of genera and species in the Ferns has always been 

 a matter of great difficulty, and of late years their splitting and chan- 

 ging has been carried to such a degree as to throw the whole nomencla- 

 ture into a state of utter confusion. The best characters are taken 

 from the form and arrangement of the sori and of their indusium ; and 

 some large genera, such as Adiant, Spleenwort, etc., are natural, and 

 readily recognized ; but in Polypody, Shield- Fern, Bladder- Fern, etc., 



