233 
are always fully evolved before the fructification makes its appear- 
ance ; their stipes is almost invariably without scales ; no part of the 
stipes of a frond appears, under any circumstances, to become incor- 
porated with the rhizome and form a portion thereof, the rhizome 
itself remaining succulent until the period of decay, when it dies at 
one extremity while vigorously growing at the other; these rhizomes 
are generally, but not always, exposed; they sometimes extend to a 
great distance beneath the ground; their direction is invariably hori- 
zontal. In Europe we have representatives of three very decided 
families of these rhizophyls, and possibly, also, of a fourth; but of the 
debateable position of certain ferns between the two main divisions 
much remains to be said hereafter, when the microscope shall have 
determined with accuracy the intimate structure of the rhizome. The 
families which call for an especial notice are, Rhizophylleew, Daval- 
lie and Hymenophyllez ; those which occupy the debateable 
ground are the Hypolepidee, which I shall place provisionally 
between Davallia and Hymenophyllum. 
Family RHIZOPHYLLEZ. 
In which the rhizome seems divided irregularly by nodes. At each 
node originates a solitary frond, “ which, after having arrived at ma- 
turity, separates by a special articulation formed between the node 
and the base of the stipes; after the frond has fallen, the node remains 
in the form of a round concave cicatrix, generally more or less ele- 
vated.”* ‘The capsules are seated on the back of the frond. It will 
be sufficient to distinguish three genera. 
A Genus Rhizophyllum. 
In which the veins anastomose, forming a kind of net-work. The 
examples are Rhizophyllum aureum (Polypodium aureum of Linneus, 
Pleopeltis aurea of Presl), R. Phymatodes (P. Phymatodes of Linneus, 
Phymatodes vulgaris of Presl). The whole of the genera Pleopeltis 
of Humboldt and Bonpland, Drynaria of Bory de St. Vincent, and Phy- 
matodes of Presl, appear to be referrible to this genus. The number 
of described species is very large, and they constitute the greatest 
ornaments of our hothouses. The frond is generally pinnatifid or 
entire, and even in this respect there is a striking uniformity through- 
out this vast natural association of species. 
* Smith uf supra. 
VOL. V. ; 2H 
