FRUCTIFICATION IN FERNS. 13 



30b. Campyloneuron has areolae, each usually bearing 

 two sori ; they are found between the parallel primary veins 

 which extend from the midrib to the margin. 



3 1 . Gymnopteris. — In this genus the sori follow the course 

 of the veins, and consequently vary with the venation, being 

 simple, forked, pinnated, or anastomose with each other. The 

 sori are non-indusiate. 



32. Notholsena. — In the cloak-ferns the sori are marginal, 

 and provided with no indusia. This genus is linked very closely 

 to Gymnopteris on one hand and to some species of Cheilanthes 

 on the other. From the latter it is separable only by the ab- 

 sence of the marginal indusium ; the two are likely to be con- 

 founded by beginners. 



33. Cheilogramma has simple fronds, the fructification 

 in a continuous sub-marginal line near the apex of the frond. 



34. Vittaria. — This peculiar genusoccupies a somewhat in- 

 termediate position between the indusiate and non-indusiate 

 genera, and while usually associated with the latter has consid- 

 erable claim to be ranked with the former. The fronds are nar- 

 row and grass like, bearing the sporangia in an intramarginal 

 groove, often more or less covered by the inroUed edge of the 

 frond. The venation is very obscure. 



35. Adiantum (Fig. 5). — The maidenhairs have a peculiarly 

 smooth foliage, and usually possess no 

 midvein. The veins are usually flabellate, 

 and after forking one or more times bear 

 the sori at their extremities. The margin 

 of the frond is refiexed, thus forming an 

 indusium which bears the sporangia on its 

 under surface. P's- s— A segment of 



Adiantum^ snowing the 



36. Pteris (Fig. 6). — In this genus, sori covered by indusia 

 7 J. ., u 1 ^i_ formed by reflexions of the 



now excludmg the common brake, the margin of thefrond-From 



otherwise free veins are united by a fili- Le Maout and Decaisne. 

 form receptacle which bears the sporangia. This continuous 

 marginal line of fructification is covered by a membranous in- 

 dusium formed of the margin of the frond. 



37. Cheilanthes. — The lip-ferns found within our limits 

 are unequally divided among four sections, all agreeing in bear- 



