THE HORSETAILS. 63 



but the fact that Equisctitm palustre is rare in the settled 

 parts of America will save the collector from making 

 many mistakes of this kind. Should he by chance 

 collect the rarer species, he will discover, by comparing 

 it with the other, that there are many small though 

 important points of difference. Although the two are 

 so much alike in habitat and structure, the stems of 

 Equisetum palustre are more deeply grooved and have 

 a smaller central hollow, the sheaths are dilated upward, 

 and the rootstock is solid, all of which are the exact 

 opposites of the conditions that prevail in the water 

 horsetail. 



The marsh horsetail is a smaller species than Equisetum 

 fiuviatile, seldom reaching a height of two feet, and, 

 though delighting in rich moist soil, is not so frequently 

 found growing in the water. The stem is slender and 

 often branched from the very base, producing regular 

 whorls of short branches. Occasionally the basal 

 branches may be much longer — perhaps two thirds the 

 length of the main stem — and may be borne half erect 

 like secondary stems. Fertile and sterile stems are 

 much alike, except that in the one the main stem is 

 terminated by a catkin, and in the other the apex ends 

 in a slender unbranched tip. 



The catkins are unusually large for the size of the 

 plant, being an inch or more long and about a third as 

 wide. They are borne above the last whorl of branches 

 on slender pedicels an inch or more long, and, as is the rule 

 among horsetails, perish as soon as the spores have been 

 dispersed. The species begins to fruit early in summer, 

 and a succession of new stems may often prolong the 

 season into autumn, though the greatest number of 

 catkins will be found early in the year. Sometimes 



