RARE FORM OF FERNS— V 



POLYSTICHUM ACROSTICHOIDES VAR. INCISUM INTER- 

 PRETED. 



On October 19, 1907, near the edge of a swamp in 

 the town of Lowman, N. Y., I found a clump of Polys- 

 tichum acrostichoides var. incisum. The lower pinnae 

 were incised to an unusual degree, several fronds being 

 cleft to the midrib, and one frond, which had been broken 

 off one-third the way from the tip, by wind or cattle 



perhaps, had its lower pinnae fully divided into auricled 

 pinnules so as to form miniature fronds with the tips 

 fruited as in the ordinary form. As the second and 

 third pairs of pinnae were in all respects like the lower 

 pinnae of typical incisum, this was evidently a case of 

 the incisum tendency carried to its logical conclusion. 



I have often wondered why incising of the lower pinnae 

 is accompanied by fruiting at their tips, and had never 

 been able to see any relation between the two modifica- 

 tions until this plant made it clear that they are two 

 manifestations of an attempt of a pinna to grow into a 

 frond. And since the resulting frond, as the illustration 

 shows, is a typical frond, fruited at the tip, and not var. 

 incisum, it seems evident that this is not a variety at all, 

 but, as Mr. Hopkins suggests in the Bulletin for Jan- 

 uary, 1907. a late growing form of the species, and should 

 be called " forma incisum:'' — E. T. Wixslow. Elmira, 

 A r . Y. 



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