Massachusetts Fern 115 



The delicate pubescence of the leaf-blade and the dark color 

 at the petiole's base are to be seen in the leaf at most if not all 

 stages of development. 



The yellowish glands have been found on the leaf-blades of 

 all the leaves examined, excepting one or two extremely young 

 ones, and offer the simplest means of distinguishing this fern 

 from D. noveboracensis and D. thelypteris at any stage of leaf- 

 development at which they are likely to be confused. 



It is often said that the venation offers an easy means of 

 distinguishing D. simulata from D. thelypteris, and this is true 

 of the venation in the mature leaves. In these, the primary 

 branches of the mid veins of the pinnae's segments are mostly 

 once forked in D. thelypteris and simple in D. simulata, except 

 in large, often toothed segments, which are examples of leaf- 

 development carried slightly further than usual and in which, 

 consequently, they are more complex. But in the early leaves 

 of both plants the degree of complexity of any of the venation of 

 the pinnae's segments is changeable, depending upon the segment's 

 state of development, and is not to be relied upon as a distin- 

 guishing characteristic until a fairly advanced stage of leaf- 

 development is reached. As the venation in both is pinnate, 

 the entire venation of the segments is formed by the lengthening 

 and branching of the branches of the midveins in the early pin- 

 nae, which takes place during the leaf-development. 



