THE SCOURING-RUSHES. 33 



sheaths, though in the latter these are shorter and paler, 

 with a black basal girdle. Equisetum l&vigatum is found 

 only in America, and is doubtless most common in the 

 Middle West, where it is often used for forage. It pre- 

 fers a moist soil, being usually found in sand or clay on 

 the borders of streams. Many facts in its life history are 

 as yet imperfectly known, and the beginner will find this 

 a species worthy of further observation. Five American 

 varieties of no especial importance have been described 

 in the Fern Bulletin. 



The Branched Equisetum. 



Students who consult other works on the fern allies 

 will find listed among the North American species two 

 that are no longer regarded as members of our flora. 

 These are Equisetum ramosissimum'&\\& Equisetum Mexi- 

 canum. The first was reported from British Columbia 

 more than fifty years ago, but as it has never been 

 rediscovered there, and the reported situation is far out 

 of the plant's known range, it seems almost certain that 

 some other species was mistaken for it. The second 

 species, Equisetum Mexicanum, has frequently been 

 reported from southern California, but here again the 

 probabilities are that the identification is incorrect. 

 Baker, in his " Hand-Book of the Fern Allies," considers 

 Equisetum Mexicanum to be a form of the tropical Equi- 

 setum giganteum ; and while it is possible that an occa- 

 sional plant of this species may stray across our south- 

 western border, it is more probable that the California 

 specimens belong to a different species. Since these 

 plants have always been wrongly identified, it becomes 

 necessary to give them a new name to distinguish them. 



