584 



THE BOOK OF CHOICE FERNS. 



is admitted, and over a score of species are referred to it. A new distinctive 

 character is also indicated : ' Pinna? (leaflets) truly articulated to the rachis, 

 and easily separated from it.' Fee divided the species into two genera, 

 Nejjhrolepis and Lejndocaulon, assigning to the former the species with 

 a broadly reniform indusium somewhat laterally attached to the receptacle, and 

 to the latter those with a round, reniform indusium, affixed by the centre ; 

 but since specimens are very common in which both forms of indusium occur 

 on the same pinna, it is clearly impossible to make the special form of indusium 

 a generic character. A peculiarity in the genus, which escaped the observation 

 of many of the earlier pteridologists, is the - indefinite groAvth of the fronds. 

 According to the observations of Mettenius, there is no necessary limit to the 

 apical development of the fronds in mature plants. What he has to say on 

 the subject is found in his ' Filices Horti Botanici Lipsiensis,' pubHshed at 

 Leipzig in 1856, where (at p. 99) he expresses himself as follows : 



" ' The rhizome (prostrate stem) of all the cultivated species is raised 

 erect from the soil, without reaching any great height, and is covered with the 

 gradually-decaying leaf-stalks. In all the cultivated species, just below the 

 points where the fronds are inserted on the rhizome, there originate filiform 

 (thread-like) runners, which either produce buds somewhere on their course 

 above ground, or develop tubers at the end which enters the soil, and thus 

 contribute to the multiplication of the plant. The fronds are characterised 

 by the perennial, indefinite growth of the rachis or leaf- stalk, and the con- 

 sequent unlimited periodical production of pinnae at the uninjured circinate 

 (crozier-like) apex, long after the older pinna? have fruited or fallen ofi^. Only 

 in the earliest fronds of plants grown from spores (and also in N. platyotis 

 \_N. acuta] and N. davaUioides, after the formation of the fertile pinnte) does 

 the development of the frond terminate with a gradual diminution of the size 

 of the pinna? , whilst the highest rudimentary side pinna blends with the proper 

 terminal segment. In iV. exaltata the oldest fronds continue to develop at the 

 apex, and the growth of the frond is limited only by some injury happening 

 to the apex. The limit of the yearly increase of the frond is always indicated 

 by the smaller size of the segments.' " 



Hooker includes Nejjhrolepis in the tribe Asjidiece, while Mettenius places 

 it in Davalliece^ and Fee locates part of it in each of these Tribes, though the 

 character of the indusium, when fully developed, is unmistakably Aspidioid. 



