GOO 



FILICES. 



Blechnum — The general involucre is referrablc to the in- 

 flexetl margin of the frond as in Pteris, in some species of 

 which, the frond is actually produced beyond the inflection ; 

 we may hence look for any amount of dislocation from the 

 costa, forming a very natural passage into Pteris. 



In no case does an involucre not having this origin, open 

 internally. 



It follows hence as a matter of course, that the intromar- 

 ginal vein is far within the margin. 



Thus a section will be formed, characterised by the prolon- 

 gation of the margin of the frond beyond the vein to which 

 will belong. 



Blechnum. 



Doodia. 



Woodward ia. 



What can be the reason that in Doodia and Woodwardia 

 the sori are not continuous, they are enclosed in Woodwardia 

 in cells, the sides of which are formed by the secondary veins, 

 which is due to the bifurcation of these. As bifurcations 

 very rarely bear sori, especially in the the congeners, it is due 

 probably to it. 



The venation of Woodwardia is remarkable, we have a short 

 secondary, with a bifurcation which runs in the direction of 

 the costa, giving off branches also on its outer edge. PI. 

 CXXXVIII. f. II. 9. these branches again are generally 

 forked and anastomose freely from the junctions to the ulti- 

 mate veins. 



The fork is equally free in Doodia, in which other sori are 

 occasionally added between the forks, (which appear to be 

 rare,) of the tertiary veins ; so that double Blechna, and double 

 Woodwardia may occur : it is curious that as the fork is so 

 constant in Woodwardia, they do not occur on it, for it cer- 

 tainly has two parallel intromarginai continuous veins. 



In Adiantum the veins of the inflected portion which are 

 capsuliferous, are obvious continuations of those of the frond ; 



