Marginal Shield Fern 121 
Range. Nova Scotia to British Columbia, south to Indian 
Territory, Arkansas, Alabama, and Georgia. 
Dryopteris marginalis (Linneus). A. Gray, Manual, ed. 1, 632. 1848. 
Polypodium marginale. Linneus, Sp. Pl. rogt. 1753. 
Nephrodium marginale. Michaux, Fl. Bor. Am. 2: 267. 1803. 
Aspidium marginale. Swartz, Syn. Fil. 50. 1806. 
THE venation of the leaf of Dryopteris marginalis is pinnate. 
The development of the leaf’s form can be seen from Pls. 
XXI, XXXII. 
It will be seen that the development of the leaf’s segments is, 
on the whole, gradual. Excepting the development of the basal 
primary segments (pinne), whose segments begin to develop 
almost coincidently with the pinne themselves, the segments 
mostly become fairly well formed before their subdivision into 
segments is more than obscurely indicated, although it is early 
suggested by minute notches occurring between their midveins’ 
primary branches. The segments of each successive series 
following the primary series start with much the same form and 
venation, and undergo, so far as their development extends, 
substantially the same changes in form and venation as those 
of the preceding series: since they are a part of those, they 
obviously cannot reach the same height of development. In 
addition, the formation of each series following the primary 
one begins on the segments first formed (lowest on the leaf’s 
stalks) of the preceding series, and involves successively the 
segments successively next formed (next lowest). As a result: 
In the older leaves, segments in all stages of development 
can be seen. For instance, tertiary segments are often to be 
seen at the base of the leaf while some of the primary segments 
(pinne) near its apex are still in the subentire state. Also, 
