farwell: genus hippochaete in north AMERICA 463 



form obsoleteness in H. scirpoides to 4/5 the total diameter of the 

 stem in H. prealta and H. laevigata. It has been suggested that 

 all variations from the two types above mentioned, in the anatomy 

 of some forms, are due to hybridization. This may be so but it 

 has yet to be proved by exact laboratory work. On the other 

 hand, varieties combining these intermediate or variable anatomi- 

 cal characters, such as H. variegata var. anceps and H. hyemalis 

 var. Jesupi are sometimes found where the supposed parents 

 have never been detected; the former on Parkedale Farm and 

 the latter on Belle Isle, an island in the Detroit River, which 

 has 5 or 6 miles of shore line with the nearest point of mainland 

 1/2 a mile away. It is the only Hippochaete that has ever been 

 detected on the island. 



In certain Californian plants Mr. Eaton ascribes to Hippochaete 

 ramosissima (Desf.) comb. nov. {Eqiiisetum ramosissimum Desf. 

 Fl. Atl. 2: 398. 1800) an anatomy like that of H. laevigata. 

 According to Luerssen the parenchyma of this species is continuous 

 thus being intermediate but more similar to that of Hippochaete 

 hyemalis (L.) comb. nov. {Equisetum hyemale L. Sp. PI. 1062. 

 1753) than to H. laevigata. If Luerssen is correct in regard to 

 the anatomy of H. ramosissima, then the Californian plants are 

 not of that species and it should be excluded from the American 

 flora. Notwithstanding that Sadebeck gives it a range on the 

 American continents from 49° north latitude to 30° south latitude, 

 it is highly improbable that it occurs north of central Mexico. 

 Judging from the anatomy, as described by Mr. Eaton, the plants 

 he referred to H. ramosissima should be referred to some form 

 of H. laevigata, probably to var. Fimstoni. 



From an intimate study of these plants in the field, extending 

 over many years, I have become thoroughly imbued with the 

 conviction that they constitute a valid genus distinct from Equi- 

 setum. The habit and other characters by which Hippochaete 

 differs from Equisetum are as constant and of as much significance 

 as those which separate Aster from Solidago in the higher plants, 

 and many other closely allied genera which could just as readily 

 be named. Generally speaking their differences may thus be 

 expressed. 



Stems annual, often dimorphous, the sterile always with regular verticils 

 of acutely angled branches at the nodes; spikes rounded at apex; 

 stomata scattered. Equisetum. 



