Horsetails Sentence Examples
The plants showing it are not all forest trees, hut include also some Pteridophytes and some of the prothallia of the Ferns, Club-mosses, Liverworts and Horsetails.
The stamens of Araucaria and Agathis are peculiar in bearing several long and narrow free pollen-sacs; these may be compared with the sporangiophores of the horsetails (Equisetum); in Taxus (yew) the filament is attached to the centre of a large circular distal expansion, which bears several pollen-sacs on its under surface.
The Ferns form the great majority of existing Pteridophytes; the importance and interest of the other groups, of which the Club-mosses and Horsetails are the most familiar examples, depend largely on the fact that they are the surviving representatives of large families of plants which flourished in earlier geological periods.
In addition to the three classes, Equisetales, Lycopodiales and Filicales, under which recent Pteridophytes naturally group themselves, a fourth class, Sphenophyllales, existed in Palaeozoic times, clearly related to the Horsetails and more remotely to the Ferns and perhaps the Club-mosses, but with peculiarities of its own demanding an independent position.
Equisetites columnaris, a common fossil in the Jurassic plant-beds of the Yorkshire coast, represents another type with relatively stout and occasionally branched vegetative shoots, bearing leaf-sheaths very like those of Equisetum maximum and other Horsetails.Advertisement
Vascular Cryptogams still include one or two large horsetails with stems over an inch thick, and also 37 species of Fern, amongst the most interesting of which are 5 species belonging to the climbing Lygodium, a genus now living in Java.
The horsetails are remarkable for the large quantity of silica they contain in the cuticle (hence their value in polishing), which often amounts to half the weight of the ash yielded by burning them; the roots contain a quantity of starch.
Taking first this most northerly locality, in Grinnell Land, we find the flora to comprise 2 horsetails, i i Conifers (including the living Pinus Abies), 2 grasses, a sedge, 2 poplars, a willow, 2 birches, 2 hazels, an elm, a Viburnum, a water-lily, and a lime.
Our modern diminutive " horsetails " with scaly leaves were represented in the Carboniferous period by gigantic calamites, often with a diameter of I to 2 ft.