66 ON GENERA AND SPECIES. 



less distance apart, and in an alternate manner on the sides 

 of the progressing axis, the foot or base of attachment of 

 the frond forming- with the node a distinct and well marked 

 articulation or joint, which ultimately becomes the point of 

 separation of the mature frond, the node remaining per- 

 manent in the form of a round more or less elevated 

 cicacrix. This mode of growth includes all Polypodiacece, 

 as restricted by me to the tribes Oleandrcp, Davallioe, Poly- 

 podece, and Platycerece. To this mode of growth I have 

 given the name Eremobrya, and in characterising the genera 

 the words vernation articulate are employed, and the pro- 

 gressing axis from which the fronds are developed surculum. 

 The number of species referable to Eremobrya, however, 

 are few in comparison with those which possess a very 

 different mode of growth. If, for example, a plant of 

 Lastrea Fili.e-mas be examined, the fronds will be found to 

 be successively produced in a spiral manner from the apex 

 of the stem, in the form of a corona or crown, and thus by 

 successive development the stem is increased in height. 

 All Ferns developing fronds in this manner, even the 

 smallest, the axis of which does not rise above the ground, to 

 lofty tree Ferns, belong to this division as also a numerous 

 class which produce fronds similar to the above, but which 

 form a decumbent stem lying on the ground or but slightly 

 inclined upwards. This I term vernation fasciculate decum 

 bent, and the preceding vernation fasciculate erect. Another 

 mode of growth is common to many Ferns, such for 

 example in Pteris aquilina^ Lastrea serra, Polybotrya osmun- 

 dacea, the fronds are normally produced alternately, in a 

 single series, from the apex of a decumbent or creeping 

 stem (sarmentum). In some cases this mode of growth 

 resembles that of Eremobrya, but from which it is quite 

 distinct, und is readily known by the vascular structure of 



