THE HORSETAILS. 65 



ject to frequent overflow. It occasionally forms thick- 

 ets, as the other species do, but appears not to be as 

 gregarious as some. In the colder parts of the Old 

 World the plant is more plentiful, but becomes rare in 

 southern Europe. Mr. A. A. Eaton notes in the Fern 

 Bulletin that the Indians of Alaska make baskets of the 

 rootstocks of some species of Equisetuni and concludes 

 that this is the one used. 



'The Shore Horsetail. 



Many botanists are inclined to question the right of 

 the shore horsetail (Equisctum littorale) to be called a 

 distinct species. It presents a most perplexing series of 

 forms and appears never to be twice alike. Now it is 

 tall and abundantly branched, like Eqinsetuvi fluviatilc; 

 again it may be prostrate or decumbent, like forms of 

 Equisctum arvense; and at other times may simulate 

 Equisetum silvaticuni or Equisetum palustre. The sheaths 

 may be appressed or dilated, the central cavity may 

 occupy one-half or two-thirds the diameter of the stem, 

 and the stem itself may be either branched or simple. 

 Still more remarlcable, the spores are abortive and have 

 no elaters, this being the only form of Equisetum having 

 this latter characteristic. All these differences seem 

 best explained by the theory that the forms given the 

 name of Equisetum littorale are really hybrids between 

 some other species, and while the author accepts this 

 theory the form is here treated as a species in order not 

 to confuse the novice, who will find it listed as a species 

 in all other American works. 



Since the varieties of the shore horsetail most often 

 resemble specimens of Equisctum fluviatilc and Equise- 



