EQUISETACEJE. 157 



Rootstock rather slender, angular, with a ring of open tubes 

 running through it, producing brown acuminated tubers. Stems 

 usually 1 foot to 18 inches high, and rarely exceeding 2 feet ; 

 remarkable for the lines of bristle-like projections on the ridges of the 

 stem; these bristles vary much in length, and sometimes are alto- 

 gether absent ; I have specimens from Kingcansie, Kincardineshire, 

 and Cullalo, Fifeshire, in which they are wanting, but differ in no 

 other respect from the ordinary form. The plant is bright green, the 

 form somewhat pyramidal from where the branches begin, which is 

 at about the 6th to the 8th internode ; the branches are always 

 arched and drooping, and the top of the stem is also drooping and 

 secund. The fertile stems are at first from 9 to 15 inches high, and 

 at that time are succulent and terminated by a spike § to 1J inch 

 long ; afterwards the branches begin to appear, and are short and 

 recurved ; the stem continues to lengthen, to become firmer, and the 

 branches to increase in size, the spike withers away ; and ultimately 

 the fertile frond is distinguishable from the barren one mainly by its 

 being truncate at the top, where usually the withered remains of the 

 spike may be found. The fertile stem is generally smooth, and the 

 first internode of the branches shorter than the stem-sheath below 

 which it is produced. 



A well-marked species, from its compound drooping branches, and 

 sheaths with the teeth combined so as to appear lacerate rather than 

 toothed. 



Wood Horsetail. 



Section III.— .ESTIT ALIA. A. Braun. 



Stems all similar, or nearly so, perishing in winter, green or 

 whitish, smooth to the touch or nearly so, branched. Stomata level 

 with the surface. Sheaths with persistent teeth. Branches in regular 

 whorls, except in depauperate specimens, with a central cavity ; 

 rarely the branches are absent. Fertile stems differing from the 

 sterile ones only in being terminated by a spike, which is perfected in 

 summer. Spike blunt or rarely slightly apiculate, usually black or 

 dark brown. 



SPECIES Y.—E Q U I S E T U M PALUSTRE. Linn. 



Plate 1892. 

 Rabenh. Crypt. Yasc. Europ. Essicc. Nos. 69, 70, 71. 



Stems all similar, perishing in autumn. Sterile stein rather slender 

 or with 5 to 12 furrows, which are rather shallow in the living plant, 

 but become deeper in dried specimens, separated by ridges which 



