HAUNTS AND HABITS OF FERNS. 3 



5. In some cases there is a tendency to variation in size 

 that cannot be referred to soil or climatic influences. The com- 

 mon grape-fern {Botrychium Virginianum) will be found in 

 some localities to vary from six inches to two feet in height, ail 

 well fruited and matured, and with the extreme sizes growing 

 within a pace of each other in the same soil and with the same 

 environment. The other species of the same genus present 

 similar variations, and judging from size and external appear- 

 ance alone, a regular gradation of forms might be arranged from 

 the most diminutive undivided forms of B. simplex to the larg- 

 est of B. Virginianum. 



6. Another tendency to variation is noticed in the forking 

 of fronds either at the summit or at the ends of the branches. 

 The hart's-tongue {Phyllitis) is frequently forked at the sum- 

 mit, the walking-leaf {Camptosorus) less commonly, while the 

 same tendency is noticed in various compound forms, as Asple- 

 nittm angustifolium, Cheilanthes lanosa, Gyinnopteris hispida, 

 Dennsiadtia, Pellcea atroptirpiirea, and others. Some of the 

 species of Botrychium show the same tendency, especially in 

 their fertile segments. It is probable that all our species will 

 be found to fork under certain conditions. More definite in- 

 formation is desirable with regard to many species that show 

 this tendency, as it doubtless involves the question of ancestry 

 of existing ferns. 



7. In those species whose sterile and fertile fronds are un- 

 like, forms often appear that are intermediate between the ster- 

 ile and fertile fronds, and sometimes even form a graded series 

 from one to the other. This is especially true of the sensitive- 

 fern {Onoclea) and the cinnamon- fern {Osmunda cinnamomecC), 

 and has frequently been the source of so-called "varieties." 

 Whether this variation arises from some peculiarity of environ- 

 ment, or from some inherent tendency to reversion toward an 

 older form, will require more extended observation to deter- 

 mine. One of the varieties of Botrychium obliquum seems to 

 have been founded on a condition which is intermediate in 

 structure between the sterile and fertile segments. 



8. In a few forms there is an apparent mimicry, one species 

 imitating another in foliage or method of fruiting. In the cin- 

 namon-fern just alluded to, which has a cinnamon-colored 



