Rev. P. Keith on the External Structure of Imperfect Plants. 253 



adapted. The following brief sketch of the external structure 

 of Imperfect or Cryptogamic plants embraces generalities 

 merely, and does not profess to enter into detail. On this 

 account we content ourselves with the old division by which 

 they are distributed into Filices, Mtisci, Hepatic*, Alga:, 

 fungi; or, in plain English, Ferns, Mosses, Liverworts, Flags, 

 Mushrooms, without entering into the detail of their several 

 subdivisions. -' '.' 



The Filices, or Ferns. — Ferns are herbaceous, and tor tiie 

 most part, stemless plants, dying down to the ground in the 

 winter, but furnished with a perennial root, from which there 

 annually issues a frond bearing the fructification. The fa- 

 vourite habitats of many of them are heaths and uncultiva- 

 ted grounds, intermixed with furze and brambles. 



Neglects* urendeijUix innascitur agris.—Hor. lib. i. Sat. in. 3/. 



But the habitats of such as are the most luxuriant in their 

 growth are moist and fertile spots, in shady and retired situa- 

 tions, as on mossy dripping rocks, or by fountains and rills ot 



water. . r 



The root of the tribe of ferns assumes a great variety ot 

 different aspects in different species. In Botrj/chium Lunaria 

 it is fibrous ; in Aspidium dilatatum it is tuberous ; and in 

 Polypodium vulgare it is creeping and covered with scales. 

 In Fteris aquilina, or common brakes, it is sometimes de- 

 scribed as being spindle-shaped ; yet this is not strictly the 

 fact If a frond is taken and pulled up with the hand, the 

 lower portion of it is, indeed, spindle-shaped ; but the real 

 root from which you have thus detached the frond remains 

 still in the soil, extending in a horizontal direction at the 

 depth of from three to four inches below the surface; some- 

 times simple, and sometimes branched, but always furnished 

 with lateral fibres. M. Du Petit Thouars regards this produc- 

 tion, not as a root, but as a peculiar organ which he calls 

 tfwche soutcrrain*, the subterranean stock. Yet what is a 

 souc/ie soutcrrain but a different name for the caudex descen- 

 ders of Linnajus, and consequently a real root; and if it is not 

 a real root, where are we to find the root of this fern i After 

 all, if botanists have agreed to call this under-ground produc- 

 tion a subterraneous stock, rather than a root, I can have no 

 objection to tlair nomenclature. 



The trunk of ferns, if trunk it can be called, is a slipe sup- 

 porting the frond, or rather the whole of the herbage is a 

 frpnd, that is, an incorporation ol stipe, leal and liuclinca- 



i Ciuude Vhyt., Sean. i. 78, !'!»• 



