BRITISH FERNS. 
irS 
ROUGH-TOOTHED HORSETAIL. 
E Q UISE TUM TRACHYODON. 
This species bears great resemblance to the Dutch 
Rush, and Sir W. Hooker considers that it holds an 
intermediate place between that species and the Varie¬ 
gated Horsetail. The sheaths are pale greenish brown 
in growth, but ultimately become black, and the teeth 
are awl-shaped. It is a rare plant, being found 
chiefly in the north of Ireland and on the banks of 
the Dee. 
VARIEGATED ROUGH HORSETAIL. 
EQ VISE TUM VARIEGATUM. 
This species of Horsetail is chiefly found on sandy 
places near the sea. The stems are freely branched 
just beneath the earth, so as to give them a tufted 
appearance. It is a dwarf plant, seldom growing 
more than a foot in height, sometimes less. The 
ridges on the stems are very prominent, the sheaths 
below pale green, ribbed and black above. The 
markings of the black ring of the upper part and the 
white margin to the teeth, with the pale green colour 
of the base, have gained for this species the name 
variegatum. Many botanists do not regard this as a 
distinct species, but only as a variety of the two 
previous ones. 
