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 Besmobrya 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 



