72 DAVENPdRT ACADKMV OF NATURAF, SCIENCES. 



^i-Yz iii^li lii"f>ail near tlie hasu, fertile l)lade ^-^ \wv\\ broad. Limestone eliffs in 

 Eastern Iowa. Hot. Gaz., /'///., igg, Plate III. 



Resembles C. rliizophylliis, Ijiit may be readily distinguished by the 

 solitary axial bundle of the stijje, destitute of the extra-fascicular scle- 

 renchyma, the thinner and narrower fronds, acute base, sim]:)ler vena- 

 tion, and short sori. The typical form has two distinct bundles at the 

 base of the stipe, which coalesce above into one ; these are accompa- 

 nied by a dark thread of sclerenchyma situated outside each bundle, and 

 usually anterior to it, which unite to form a single thread after the union 

 of the bundles, or, when lateral, remain as distinct lateral threads. In 

 the variety the bundle is sim]>le throughout, and has no external scle- 

 renchyma. Again, in the ty])ical form the base of the frond is never 

 strictly wedgj-shape, as in the variety, but, however much reduced, has 

 still some indication of auricles. It is the opinion of Mr. (Jeorge 

 E. Davenport (in litt. ) that this "is only a weakly growth, in which 

 the plants have simply failed to develop their full characters," a con- 

 clusion which some of the facts do not appear to corroborate. The 

 small area covered by the plants was within a few yards of as large 

 and thrifty a growth of the tyi)ical walking-leaf as one is likely to 

 find. Small plants have been gathered by the writer and others in 

 various parts of the State, but none of them show the distinctive char- 

 acters of the variety. A specimen in the herbarium of the Chicago 

 Academy of Sciences, collected by A. H. Curtiss in Virginia, more 

 nearly approaches the variety in external ai)i)earance than any other 

 yet seen by the writer; the fibro-vascular bundle, however, is in every 

 respect typical. If this be only an individual form, it is sdll interest- 

 ing, as all the deviations from the type are in the direction of the Sibi- 

 rian species, C. Silnricus, the only other species known. The walking- 

 leaf is not a rare fern in Iowa, and the discovery of the variety in other 

 localities may confidently be expected. 



Corrections and Kxim.anaiions. 



The following are corrections of jirevious contributions and some 

 additional notes on the ])resent one: 



In Contr. No. V., for Emiiiett Co., read Emmet Co. 



AphvUoii fasciculatuin (No. 523) is to be dropi)ed from the catalogue. 

 Upon re-examination, the specimens prove to be the same as No. 522=' 

 of Contr. No. II. It {A. toiiflonim, T. & Cx.) is a very rare plant in 

 the State. 



