LIBRARY 



NEW YORK 



BOTANICAL 



"t* '» * ■ *J A R E 



THE FERN BULLETIN 



VOL. VII. JULY, 1899. NO. 3. 



THE GENUS EQUISETUM WITH REFERENCE TO THE 

 NORTH AMERICAN SPECIES. 



By Alvah A. Eaton. 



THIRD PAPER. 

 HippocH.tTE Milde. 



S TOM ATA forming two exceedingly regular rows in the 

 grooves, vertical, separated from each other by regular 

 quadrate cells, lying in a deep depression of the epidermis, 

 overlaid with a silicious plate, which is continuous with the epi- 

 dermis and penetrated by an irregular opening. Plants not 

 dimorphous ; branches with central cavity, first internode always 

 shorter than sheath of stem; spike pointed; rhizome roughened 

 with silicious points. Species not easily separated. 



A. Equiseta ambigua Milde. 

 Rows of stomata in 1-4 lines ; plants of various aspect, small 

 or stout, branchless or branched, according to locality or other 

 causes; ridges rounded; sheaths elongate, widened at top; 

 branches at most 4-9 angled. 

 (8.) E. ramosissimum Desf. 



B. Equiseta monosticha Milde. 

 Row of stomata of 1 line ; plants of various aspect, as regards 

 size and branches; ridges convex or grooved. 



a. Equiseta hiemalia Milde. 

 Ridges 2-angled; plants almost always branchless; sheaths 

 mostly cylindrical, appressed ; teeth mostly deciduous. (9.) E. 

 hiemale L. (10.) E. robustum A. Br. (11.) E. Iczvigatum 

 Al. Br. 



b. Equiseta trachyodonta Milde. 

 Ridges angled, very broad, concave; grooves covered with 

 rosettes; sheaths widened, seldom appressed; teeth not decid- 

 uous, grooved, rough. Plant branchless in normal condition, 

 (12.) E. variegatum Schleich. (13.) E. scirpoides Michx. 



