Narrow-Leaved Spleenwort 65 



Range. Northern New England and southern Quebec to 

 Wisconsin, south to northern Georgia, Tennessee, and Missouri. 



Asplenium angustifolium Michaux, Fl. Bor. Am. 265. 1803. 



THE young leaves of Asplenium angustifolium are translucent 

 when dried. The venation can be seen distinctly by transmitted 

 light, and the development of the vascular system easily observed. 



At first only one fibro vascular bundle is present in the leaf's 

 petiole : it may perhaps sometimes divide into two at the extreme 

 base of the petiole. Soon two are seen, which merge into one 

 some distance above the base. The mature petiole contains two, 

 which coalesce to form the leaf-blade's primary midvein. 



The venation is pinnate. The translucence of the young leaf 

 reveals the fact that a pinna's midvein sometimes leaves the 

 midvein (fibrovascular bundle) from which it springs some 

 distance below the apparent node of the pinna. 



The formation of the pinnae is gradual. The pinnae appear 

 first as small lobes, on the lower part of the leaf's apical section 

 in the older leaf and substantially at the leaf's apex in the younger. 

 New lobes begin to form above those previously formed while the 

 latter are separating to constitute pinnae. This will be seen from 

 Plate XIV, and it will also be seen that both the pinnae and the 

 leaf -blade itself are short and blunt at first, but gradually lengthen 

 and become pointed more and more. 



In some leaves of this fern, collected in Vermont by Miss 

 Mary E. Bidwell,* there are small lobes on the lower parts of the 

 pinnae, indicating a tendency to produce secondary pinnae. Some 

 of the basal lobes in these leaves are distinct. This seems to be 

 a case of monstrous leaf-development. Spores from these leaves 



* See Fern Bulletin, 8: 61. 1900. 



