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 angustijolium 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 fibrovascular 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 pinne is gradual. The pinne 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 pinne. This will be seen from 
Plate XIV, and it will also be seen that both the pinnz and the 
leaf-blade itself are short and blunt at first, but gradually lengther 
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 
pinne, indicating a tendency to produce secondary pinne. 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. 
