THE SCOURING-RUSHES. 29 



grooves each. At the same time, an Eqitiscliim was 

 found near Joliet, Illinois, that differed so constantly 

 in these characters that it was considered a new species 

 and was named Equisetiun Fcrrissi. This species is 

 principally distinguished by its tall, slender, pale-green 

 stems Avith few grooves, and the exceedingly long 

 sections between joints. IMore than fifty specimens, 

 selected at random, were measured, and all but four 

 were 4/32 of an inch or less in diameter. The grooves 

 were also fewer in number, only nine stems having more 

 than fourteen grooves. The greatest difference of all, 

 however, was in the length between joints. None of 

 the internodes were as short as the average in Equisetiun 

 hiemale, and but fourteen were less than four inches long. 

 The longest measured more than six and a half inches. 

 This form may also be known by the appressed sheaths, 

 which are green when young, but in age become chalky- 

 white with a narrow black basal band encircling them 

 obliquely. The teeth are two thirds the -length of the 

 sheaths, slender and deciduous, with a central streak of 

 dark brown bordered by a wider hyaline margin. After 

 the teeth have fallen, the border of the sheath becomes 

 thickened, incurved, and dark brown in colour. The 

 grooves between the leaves extend below the basal black 

 band. The catkins, lilce those of the common scouring- 

 rush, are tipped with a sharp point and are borne on a 

 short pedicel. They ripen about the first of June, but 

 many appear to be abortive and are to be found in the 

 globular expansion formed by the topmost whorl of 

 leaves. 



The slender scouring-rush resembles Equisetmn hiemale 

 intermedium, but may be distinguished from it by the 

 smoother, slenderer stems, by having fewer grooves in 



