TI1E POLYPODIES. 29 



frond take their rise, but this feature is much more obvious 

 111 P. Dryopteris. The fronds are divided so that each branch 

 is pinnate at the base, and pinnatifid towards its point ; the 

 pinnae are also pinnate at their base, then pinnatifid, becom- 

 ing acute and nearly entire at the point ; the pinnules and 

 ultimate lobes are oblong and obtuse. The pair of pinnules 

 at the base of each pinna, close to the principal rachis, are 

 placed so that when the pinnae are exactly opposite they 

 stand in the form of a cross ; the two towards the apex of 



FIG. 2. 



Polypodiiem Dryoptorit. 



the branch being smaller than the opposite pair, and more 

 nearly parallel with the rachis. The pinnules, or lobes, have 

 a rather wavy midyein, from which the venules branch out 

 alternately, being, in those of moderate size, simple, with a 

 sorus near their extremity, and in those which are larger and 

 more compound, branched, with a sorus on the lower branch. 

 The fructification is very unequally produced in different 

 seasons and localities, being sometimes crowded, and at other 

 times very sparingly scattered over the fronds. 

 This is at once known among the Polypodies by having 



