60 FERNS : BRITISH AND FOREIGN. 
Endogen. The terms equivalent to the two latter are 
Pleurogen and Acrogen. 
In Eremobrya the fronds are produced singly from 
the sides of a rhizome, which has its growing-point 
always evidently in advance of the young developing 
frond. Each frond springs from a separate node, 
more or less distant from its neighbour, and is there 
articulated with the rhizome, so that when it has 
passed its maturity it separates at the node, and 
leaves behind a clean concave scar. The rhizome is 
solid, fleshy, and brittle, and when young always 
densely covered with scales (excepting in hypogeous 
rhizomes), which seldom, except in the very few scaly- 
fronded species, extend higher than the node ; but it 
varies in some respects, being in some cases long and 
slender, and either simple or branched, and in others 
short and thick. The essential distinction between 
Eremobrya and Desmobrya rests in the fronds of the 
former being articulated with the axis, while those 
of the latter are adherent and continuous with the axis. 
In Desmobrya the fronds are developed in two modes. 
In a large number of Ferns belonging to this division 
they come out from the apparent apex of the axis in 
a spiral series, and form a fascicle or corona. In this 
case the axis or stem is an erect or decumbent caudex, 
very variable in size, being sometimes scarcely elevated 
above the ground, and sometimes, in extreme cases, 
rising to the height of fifty or more feet. Almost an 
equally large number, however, have their fronds de- 
veloped in a single alternate series, and their stem 
forms a sarmentum, in which the point of growth is in 
most cases scarcely at all in advance of the develop- 
ing frond, and would appear to be coincident with 
