166 ABOUT HORSETAILS, [CHAP. 
There are but ten British species, six of which are 
to be obtained in the London district. Some of them 
being very beautiful objects, might well be admitted 
to a place in the fernery, all that they require being 
plenty of moisture. The one thing to be sure of is, 
that the underground stem is obtained with its root- 
lets intact; it will then grow freely. Some of the 
species have the additional recommendation of being 
evergreen, though the deciduous kinds rival them in 
elegance. 
The distribution of these remarkable plants is 
almost world-wide, some of the species attaining a 
considerable size; but they cannot approach the 
dimensions attained by representatives of the order 
in past ages. In the forests of the Carboniferous 
Period—when our coal was being formed—immense 
horsetails were abundant, reaching the height of 
thirty or forty feet, with a circumference of about 
fifteen inches! The remains of them have been 
found as fossils in the coal, and the name of Cala- 
mites applied to them. 
“ There is no doubt now that they are of the same 
family as our Equiseta, or Horsetails, a race which 
has, over most parts of the globe, dwindled down now 
from twenty or thirty feet in height, as they were in 
the old coal measures, to paltry little weeds. The 
tallest Equisetum in England—the beautiful &. Ze/- 
mateia—is seldom five feet high. But they, too, are 
mostly mud and swamp plants, and so may the Cala- 
mites have been.’—Kuingsley, “ Town Geology.” 
Somewhat resembling the Horsetails in appearance 
is a small tribe of delicate aquatic plants known as 
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