535 



fibrillae. The rhizoma is creeping, and extends to a great length ; it 

 is of nearly the same diameter as the stem, very black and shining, 

 and smooth to the touch : at the joints it is solid, but the internodes 

 are more or less hollow. 



The engraving at the head of this article represents a stem of marsh 

 horse-tail of the normal size and proportions : in order to exhibit the 

 whole at one view, the stem has been divided into three portions. — 

 The stem is perfectly erect, about fifteen inches high, deeply farrowed 

 and finely granulated : the furrows are eight in number, the granula- 

 tions of the ridges between them feel rough to the edge of the nail if 

 drawn along them. The stem is divided into eleven compartments 

 by means of transverse septa ; the internodes are an inch and a quar- 

 ter or an inch and a half in length : the sheaths occur at the septa, 

 and correspond in number ; they considerably exceed the stein in cir- 

 cumference, and in consequence are loose : the ridges of the stem en- 

 ter the sheaths and terminate in the teeth, which are eight in number, 

 acute, wedge-shaped, tipped with black, and furnished with nearly 

 transparent membranous edges. There are nine whorls of branches: 

 these rise from the furrows of the stem, close to the base of the 

 sheaths ; they never exceed the furrows in number, and are frequently 

 fewer ; at the base of each is a short black sheath, and these form a 

 series of black rings round the stem : they are divided into six or 

 eight joints, of which the basal and apical are the shortest : they have 

 five furrows, and the sheaths occuning at the joints are five-toothed; 

 the teeth are tipped with brown : the branches vary in length in the 

 same whorl, and still more so in different whorls. 



The catkin is long and rather naiTow ; when mature it stands on a 

 distinct stalk of its own length : it is terminal, and after discharging 

 its seeds it appears to perish, the stem and branches continuing to 

 retain their vigour. There is no apiculus, the extreme summit being 

 composed of a scale similar to the rest: at first the scales are crowded 

 together, forming a black mass, they afterwards separate, the peduncle 

 supporting each becomes visible, and the catkin, increasing in length, 

 assumes a brown colour. The catkin appears in May and June. 



This species, like the preceding, is subject to extraordinary varia- 

 tions, the most striking of which I shall describe. 



Edward Newman. 



(To be continued). 



