GENERA OF FERNS AND THEIR CLASSIFICATION. Cl 
it, though sometimes the prolongation is evidently in 
advance, and then the mode of growth appears to 
agree with Eremobrya ; but the non-articulation of the 
stipes at once distinguishes it. Whatever the character 
of the stem of Desmobryous Ferns, it is always formed 
of the united and adherent bases of the fronds, and 
increases by the successive evolution of fresh fronds, 
each succeeding one of which is produced on the 
interior side of the bases of the preceding ones. 
All Ferns are referable to one or other of these 
two divisions, and in general the difference between 
them is readily seen, particularly when living plants 
are examined ; but, as in all attempts to generalize 
from special organs or structures, there are exceptions. 
For example, in Elaphoglossum the fronds are neither 
strictly adherent nor strictly articulate, but have a 
swelling some distance up the stipes, at which point, 
though there is no change in structure, the vascular 
bundles are so weak that the fronds ultimately sepa- 
rate there; and hence I regard the genus as an 
aberrant form of Desmobrya (?). In Woodsia, again, 
the stipes has an elevated articulation ; but the axis is a 
caudex formed of the adherent bases of the stipes, and 
this, together with its fasciculate frond, indicates its 
true affinity to be in Desmobrya. A few also occur, 
as in the section Gtenopteridece of the tribe Polypodies, 
in which the articulation is obscure, and a careful 
examination is required to detect it. 
Notwithstanding these few exceptions, there can be 
no doubt that the two modes of growth above de- 
scribed are widely distinct, and the two groups into 
which Ferns are thereby divided are quite distinct in 
habit and appearance. The plants too seem to be 
