62 THE HORSETAILS. 



is often found in mud or moist sand and gravel at mid- 

 summer, owing to the lessening of the water by drouth. 

 Along certain rivers it forms a continuous border for 

 miles, almost to the complete exclusion of other plants. 

 It occurs also in northern Europe and Asia, belting the 

 earth in a zone nearly a thousand miles wide. It is a 

 polymorphic species and in some of its disguises is hard 

 to identify. Its irregular branching and appressed 

 sheaths are most characteristic features. It is so much 

 like the marsh horsetail and the shore horsetail in 

 appearance that the novice may have trouble in dis- 

 tinguishing between them, but since this is the only one 

 of the trio that is abundant it is safe to give it the 

 benefit of any doubt that may arise. 



In many books the species is called Equisctwn limosmn, 

 but fluvial 'He is the older name. This difference in age, 

 however, well illustrates the small differences that govern 

 the work of botanists. The name fliiviatile stands just 

 before limoswn in " Species Plantarum " and is, therefore, 

 older by the mere length of time it takes for the printer 

 to set a line of type ; and yet this is held sufficient to 

 make the one for ever right and the other for ever wrong. 

 Liinosum is now used to characterize the nearly un- 

 branched form. Among its common names are " mud 

 horsetail," " joint-grass," and " paddock-pipes." The 

 last name is also given to Equisetum arvensc, but is more 

 appropriately applied to this species, since it is found 

 in the places beloved of " paddocks," as frogs were 

 commonly called. 



The Marsh Horsetail. 



At first glance it is possible to mistake the marsh 

 horsetail (Equisetum palustre) for the water horsetail, 



