Maidenhair 35 



or the smaller sublunulate, yellowish-brown, slightly striate; at 

 margin whitish, thin, membranaceous, somewhat erose or slightly 

 denticulate. 



Spores spheroid-tetrahedral, the three radiating angles marked 

 with slender vittse or bands. 



Habitat. Rich woods, shaded banks, etc. 



Range. Nova Scotia to British Columbia, south to Georgia, 

 Mississippi, Arkansas, Kansas, Utah, and California. Also in 

 Alaska. 



Adiantum pedatum. Linnaeus, Sp. PI. 1095. 1753. 



THE petioles and rachises of Adiantum pedatum are dark- 

 colored in all stages of development. In the earliest stages 

 they are hair-like. 



The leaf-blade is simple at first (PL II, Fig. i a, a). It 

 soon develops into a blade consisting of a single rachis leaf- 

 let-bearing at sides and apex (Figs. 2-6). First one and then 

 the other of the two basal leaflets on this rachis then develop 

 into a branch, which consists of a similar leaflet-bearing rachis 

 (Figs. 76, c; 86', c'). The outer basal leaflet (Fig. Sd) of the 

 first branch (Fig. 8 b') then develops likewise into a branch (PI. 

 Ill, Fig. qd'). In this way the earliest dichotomous leaf-blade is 

 formed (PI. Ill, Fig. 9). This may be said to consist of a di- 

 chotomous rachis (Fig. 9 e' o' j f ) bearing two pinnae at each of 

 its two apices. 



The leaflet that was formerly the inner basal leaflet g of the 

 branch b' in Fig. 8 (PI. II), becomes, when the outer basal leaflet 

 d in Fig. 8 develops into the branch d' in Fig. 9 (PI. Ill), the 

 leaflet g' on the section V o' of the dichotomous rachis e' o' }' in 

 Fig. 9, since e' o' in Fig. 9 corresponds to e o in Fig. 8. As no 



