EQTJISETUM. 245 



edges ; the teeth frequently adhere together at the summit 

 in twos and threes. The branches have eight or ten ribs 

 united in pairs, and their sheaths terminate in four or five 

 teeth, each extended into a slender black bristle, and having 

 two denticulated ribs. The branches very frequently pro- 

 duce a series of two to five secondary branches at their 

 second joints. The colour of the main stem is very pale, 

 scarcely tinged with green, that of the branches a delicate 

 green. The sheaths of the branches, in this and some other 

 species, furnish excellent marks for discrimination. 



The fertile stem is erect, simple, from nine inches to a foot 

 or more high, succulent, pale brown, and smooth. From 

 each of the numerous joints arises a large loose funnel- 

 shaped sheath, the upper ones being largest ; they are dis- 

 tinctly striated, and terminate in thirty to forty long, slen- 

 der, and, according to Hooker, two-ribbed, teeth. The 

 sheaths are pale greenish-brown below, darker brown above. 

 The catkins are large, between two and three inches long ; 

 the scales, often numbering four hundred, are arranged in 

 whorls, of which the lower ones are usually very distinct. 

 The scales and spore-cases resemble those of the allied kinds. 



A section of the barren stem of this species shows an outer 

 surface without ridges and furrows, and in the very narrow 



