88 Christmas Fern 



primary branch of the pinna's midvein. This auricle some- 

 times, in very highly developed leaves, actually becomes a pin- 

 nule, as will be seen further on. The lower basal sides of the 

 pinnae mostly remain more or less oblique to the rachis. 



The early leaves are crenately toothed or lobed, but one or 

 more spinulose or at least apiculate lobes are usually to be seen 

 before the first pair of pinnae becomes distinct. More spinulose 

 points appear in subsequent leaves, until the blunt teeth or lobes 

 are almost or quite superseded. Each spinulose point occurs 

 at the apex of a veinlet of the leaf, but one is not present at the 

 apex of every veinlet. In the later leaves there is usually one or 

 more to every primary branch of the pinnae's midveins. 



The leaf becomes fertile first above and the fertile pinnae 

 are contracted. 



In some plants, some or all of the leaves become very highly 

 developed, with the following results. In the fertile leaves the 

 soriferous zone extends downward, forming a sort of triangle, 

 the pinnae, like the leaf-blade itself, becoming soriferous first 

 at the apex, and their soriferous parts mostly becoming con- 

 tracted. Incisions occur between the primary branches of the 

 pinnae's midveins and sometimes deepen sufficiently to render 

 the leaf subbi pinnate. These primary branches, constituting 

 the midveins of the pinnae's segments, are more complex than 

 in the usual pinnae. 



The so-called "vars." " schweinitzii " Beck, and "incisum " 

 Gray, are based on these highly developed leaves. These leaves 

 are usually very large and densely soriferous, and, as Mr. A. A. 

 Eaton has pointed out, appear to be the product of extreme 

 luxuriance of the plant. From the following facts and from my 



* See Fern Bulletin, 8: 13. 1899. 



