PERN-TYPES. 



23 



" In most Ferns, however, the divisions of the frond are traversed by several or many 

 veins. When they are forked primary veins, diverging from each other in a radiate 

 manner, and equal, or the central one more prominent, the venation is Ci/clojjferis (fig. 3). 

 This is divided into several types, of which I will explain the C. simplex cequalis, the C. sim- 

 plex incequalis, and the C. composita. In the first the primary veins are symmetrically 

 disposed, forming only forked branches {ex. Adianticm) ; in the second the primary 

 veins are nearly all on one side of the division, or iinsymmetrically dispersed ; and in 

 the last the primary veins send out secondary ones, as in Lygodium. 



Fig. 1. — Uvpliopteris. 



Fui. 2. — Craspedopteris. 



" In ail other khids of venation of Ferns, each ultimate division has only one primary 

 vein (the midrib or costa) from which the secondary ones spring, and the latter 

 frequently give rise to ternary veins. 



" TUie primary vein rarely reaches the apex of the pinnule in Neuropteris (fig. 4), but 

 disappears in a number of forked branches, and the secondary veins are given off from it at 

 very sharp angles, diverging in curves towards the margin, so that their marginal branches 

 constantly form more obtuse angles with the primary vein than their stems. Among the 



Fig. 3. — Cyclopteris. 



Fig. \. — Neuropteris. 



types of this kind of venation we notice the Neuropteris vera ; here the midrib is 

 invariably dissolved, and usually at an appreciable distance from the apex, and the 

 dicliotomously branched secondary veins diverge very much. In N. acrosfichacea the 

 primary vein is prolonged almost close to the apex, or even reaches it; and the 

 secondary veins are only once or twice forked, and are less divergent {ex. Pteris eocanica, 

 &c.). 



