— 6i — 



justified in accepting it in place of Michaux's thelypteroides, pub- 

 lished two years later. Swartz, however, in his Synopsis Filicum 

 (1806), after repeating his early diagnosis (p. S2) publishes a fuller 

 description (p. 275) and assigns a definite locality to the fern. 

 The longer description points definitely to our plant of eastern 

 North America, and it seems but just to interpret his early charac- 

 terization in the light of his amended description, even though 

 Michaux's name had been published in the interim. There is of 

 course the alternative of holding to Michaux's as the first recog- 

 nizable diagnosis, in which event Athyrium thelypteroides 

 (Michx.) Desv. should be taken up. The fact that in 1S36 the 

 name Athyrium acrostichoideitm Bory was published, applied to a 

 wholly different plant, does not, according to current practice, 

 militate against the transference of Swartz's specific name to the 

 genus Athyrium. 



THE GENUS EQUISETUM WITH REFERENCE TO THE 

 NORTH AMERICAN SPECIES. 



By Alvah A. Eaton. 



HIZOME 7 angled, shining brown or black, without felt or 



tubercles i*< "-6 " thick, solid at center.but with large vallecu- 



lar cavities separated by dissepiments only two cells thick. 

 Fertile and sterile stems alike, save that the former is terminated 

 by a fruit-spike about 1 long, raised on a short pedicel. They are 

 prominently 5-10 angled, usually naked and nearly smooth below, 

 branched and rough above, with distinct irregular cross bands of 

 silica traversing the ridges and grooves; ridges narrow, sharply 

 elevated but rounded on the back, ' { as broad as the deep 

 grooves; stomata abundant, usually broadly oval, disposed in a 

 broad irregular band of 10 to 12 rows; sheaths gradually widen- 

 ing upward, green or variously marked with brown or black, 

 leaflets convex, keeled below the middle with a distinct carinal 

 groove which extends into the teeth. Teeth broadly lanceolate' 

 sharply pointed, usually black, with a broad white hyaline border. 

 Branches 4-7 angled, rough with abundant cross bands of silica; 

 teeth and sheaths similar to those of the stem, but the latter 

 usually green, the former deltoid or narrowly lanceolate, with a 

 carinal groove. A section of the stem shows all three kinds of 



EIGHTH PAPER. 



E. Palustre L. 



