MARSH HORSETAIL. 113 



ridges are not sharp at the apex. The stem is rather rough to 

 the touch, in which respect it can be at once distinguished from 

 the Mud Horsetail, which grows in similar situations and is 

 quite smooth. The sheaths are short and rather "closely 

 pressed to the stem, their teeth sharp pointed with dark-brown 

 thin tips. The branches are all curved upwards, the lowest 

 whorl also the longest, succeeding whorls gradually less until the 

 uppermost are mere protuberances. The barren stems end in 

 a tapering whip-like length of several naked joints ; the fertile 

 in the short blunt cone, which is ripe in June and July. In 

 our photograph of this species, both the shortest and the 

 longest stems will be seen to bear cones. (Plates 120, 123, 125.) 



There is a form, known as van polystachya^ in which the 

 branches also bear cones at their tips. 



A cross-section of the stem shows a very small central cavity, 

 as compared with the other species. In the fleshy cylinder 

 there is a series of small circular tubes, and outside these eight 

 or nine much larger shield-shaped cavities. In this respect the 

 structure is much like that of the Wood Horsetail, but both the 

 external and internal margins are different in that species. 



The Marsh Horsetail is common in wet places throughout 

 the United Kingdom and in the Channel Islands, and it 

 ascends the Highlands to an elevation of 2500 feet. It is also 

 found throughout Europe, North and West Asia, and in North 

 America. .The English name is probably of book origin, but 

 the local folk-names include Marsh-weed ; other local names are 

 Cat-whistles probably suggested by the hollow joints of the 

 stem, and of similar origin is Snake-pipes, and the Scotch name 

 of Paddock or Puddock-pipes. Snake-pipes is common to this 

 and the Field Horsetail, and Paddock-pipe in various forms 

 is also bestowed on the next species. Palustre is a Latin 

 adjective signifying growth in fenny or marshy places. 



