19 1 7- Praegek — Equisetitm litorale in Ireland. 145 



wein/ first described (as a species) from Russia. This 

 plant has been much discussed since its discovery, and 

 possesses a quite extensive hterature. To mention the 

 views of two leading authorities on the Equisetaceae, Duval- 

 Jouve awards it specific rank, while Milde comes to no 

 final conclusion, though pointing out the strong evidence 

 for its being a hybrid, E. arvense x limosiim. Recent writers 

 generally accept the latter view of its position, which is 

 much strengthened by the fact that the spores are abortive 

 and the elaters absent — the latter feature I was able to 

 confirm in the Hilltown specimens. For full descriptions, 

 discussions and figures of the plant, with synonymy, <^c., 

 the monographs of the two writers quoted above^ should 

 be consulted. E. litorale, which has been characterized 

 by Milde as " one of the most remarkable of cryptogams," 

 is the only known hybrid Equisetum ; and for a hybrid it 

 has a very remarkable geographical range, occurring in 

 northern, central and western Europe, Bulgaria, Canada 

 and the United States. In England, it was discovered at 

 Bisley, Surrey, by W. H. Beeby in 1885 (Journ. Bot. 24, 54), 

 and described and figured in the same Journal soon after- 

 wards (25, 65, tab. 273). Bisley has since remained the 

 only British station. Eqtdsetum litorale is, like several 

 others of our British Horsetails, an extremely variable 

 plant, and it varies in the same directions — size, habit (erect 

 to prostrate), branching (simple to much branched), the 

 bearing of lateral as well as terminal cones, and so on. 

 Milde enumerates four varieties and seven monstrous 

 forms, and to these several other " varieties " have been 

 added by A. A. Eaton, from American material ; but as 

 these variations are dependent chiefly on habitat, they have 

 not much importance. The Bisley plant is described as 

 passing gradually from var. gracile to var. vulgare Milde — 

 that is, from a small unbranched to a larger branched 



* Kuhlewein in Ruprecht, BeitrSge zur Pflanzenkunde des russischen 

 Reiches, iv. Lieferung, p. 91. 1845. 



2 DuvAL-JouvE : Histoire naturelle des Equisetum de France. 1864. 

 Milde : Monographia Equisetorum, in Nova Acta x\cad. Nat. Curios. 

 23, 2 Abth. 1867. 



