THE BRITISH HORSETAILS. 115 



remarkable has been called polystachyon, and is remarkable 

 in having more or less of the branches of the two upper 

 whorls -^terminating in cones of fructification ; the usual 

 habit of the plant being to produce only one cone, and that 

 on the central stem. It has been suggested that the produc- 

 tion of these lateral fructifications is accidental, owing to 

 the destruction of the top of the main stem, but this expla- 

 nation is quite insufficient, since they are sometimes produced 

 along with the central head, which moreover vanes when 

 accompanied by them, being sometimes of the usual size, 

 and sometimes reduced in size like the lateral heads. The 

 lateral heads are usually later in their appearance than the 

 central ones. Occasionally some of the branches of the 

 lowest whorl become elongated, and terminate in these small 

 cones. 



Another form, called nudum or alpinwn, is a depauperated 

 form, differing from the ordinary plant in being altogether 

 smaller, the height ranging from two to four or five inches, 

 the lower part of the stems being decumbent, and the whole 

 stem almost devoid of branches ; a few being developed only 

 at their very base. In some states, this form has much re- 

 semblance to the prostrate E. variegatum, but is distinguish- 

 able by means of its sheaths and fructification. 



THE LONG ROUGH HORSETAIL, 



This species is by botanists called E. ramosum, and has 

 been in this country also known as E. elongatum and E. 

 Mackayi. It is one of those species in which the stems that 

 produce the fructification, and those which are barren, do 

 not differ in any other respect, and are therefore said to be 

 similar. The stems also are almost branchless, the branching 

 being mostly confined to the production of one or two erect 

 lateral stems from near the base, and this lateral branching is 

 by no means common. Sometimes, indeed, the upper part of 

 the stem is also sparingly branched, but the branches are 

 produced singly from the joints. The stems are slender and 

 erect, from two to three or four feet high, deeply furrowed, 

 with a double row of elevated points along the ridges, which 

 are usually from eight to twelve, but sometimes fourteen in 

 number. The sheaths are close, cylindrical, and striated 

 like the stem, terminating in a number of teeth equalling 

 the striae ; these teeth are long, slender, awl-shaped, black 

 with pale membranous margins, and usually, but not always, 

 persistent. The sheaths are, for the most part, entirely black, 

 but here and there they occur with a narrow greyish ring. 



H2 



