BRITISH FERNS. 



61 



In the neighbourhood of waterfalls, and other damp situations, 

 the plant becomes more elongate and luxuriant, and is then the 

 Aspidium dilatatum concavum of Babington, a name, by the way, 

 of great excellence, and highly expressive of the peculiar 

 character of the plant. 



The types of form of this fern may be considered as four. 



1. The linear type : erect, rigid, pale sickly green, lateral 

 margin of the frond nearly linear, figured at page 58, and the 

 spinulosa of London Herbaria : it is sometimes much narrower, 

 and the pinnae point more upwards than in the figure. 



2. The dwarf type : dwarf, nearly erect, rigid, dark green or 

 brown, lateral margins nearly linear, all the divisions having a 

 tendency to become convex above ; figured at page 60 (the upper 

 figure) ; this is the dumetorum of London Herbaria. 



3. The triangular type : drooping, deep full green ; broadly 

 triangular, the divisions having a tendency to become convex 

 above ; figured at page 59 : this is the dilatata of London 

 Herbaria. Note. It is extremely easy to find a complete series 

 of intermediate fronds connecting these three types of form. 



4. The concave type : when 

 luxuriant, drooping; when starved? 

 more erect : triangular, bright beau- 

 tiful green, all the divisions concave 

 above ; figured at page 60 (the lower 

 figure) : this is the dumetorum of 

 Smith and Mackay ; the recurvum of 

 Bree (concavum of Babington), which 

 I consider identical, is figured oppo- 

 site. 



In every variety of this species, 

 the lateral veins are placed alter- 

 nately on the midvein, after leaving 

 which, each sends out an anterior 

 branch, which bears a nearly cir- 

 cular mass of thecae half-way between 

 its origin and extremity ; all the veins terminate before reaching 

 the margin: the masses are covered by a loose reniform in- 

 dusium, which is attached on one side ; it is soon lost among the 

 growing thecae. 



