Marginal Shield Fern 121 



Range. Nova Scotia to British Columbia, south to Indian 

 Territory, Arkansas, Alabama, and Georgia. 



Dryopteris marginalis (Linnaeus). A. Gray, Manual, ed. i, 632. 1848. 

 Polypodium marginale. Linnaeus, Sp. Pi. 1091. 1753. 

 Nepkrodium 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 Pis. 

 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 (pinnse), whose segments begin to develop 

 almost coincidently with the pinnas 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 

 (pinnse) near its apex are still in the subentire state. Also, 



