. The classification of flowering plants. Plants. URTICACEAE 47 Family II. URTICACEAE The plants are generally herbaceous, as our nettles, or sub-shrubby, rarely forming a bush or tree, as in some tropical genera. The leaves are simple, with sometimes an alternate, sometimes an opposite arrangement; in the same plant they may be alternate on the stem and opposite in the inflorescence. With a few exceptions, for instance, our native PeUitory (Parietaria), stipules are present and their various positions afford marks for distinguishing genera. Thus they are attached on the base of the leaf-stalk
. The classification of flowering plants. Plants. URTICACEAE 47 Family II. URTICACEAE The plants are generally herbaceous, as our nettles, or sub-shrubby, rarely forming a bush or tree, as in some tropical genera. The leaves are simple, with sometimes an alternate, sometimes an opposite arrangement; in the same plant they may be alternate on the stem and opposite in the inflorescence. With a few exceptions, for instance, our native PeUitory (Parietaria), stipules are present and their various positions afford marks for distinguishing genera. Thus they are attached on the base of the leaf-stalk, or stand separate at its side, or in the leaf-axil (intrapetiolar). In the last case the two stipules may be more or less completely Fig. 13. Cystoliths in Urticaceae. A. Epidermis of Boehmeria, cut vertically, shewing one cell with a cystolith, highly magnified. B, C, D. Surface-views of pieces of leaf of species of Laportea, Pellionia and Pilea respectively, shewing various forms of cystoliths, magnified. (A after De Bary; B, C after Weddell.) The milky latex so common in the next family is absent. The fibres of the bast are generally of considerable length, free laterally and firmly attached end to end and hence of great value for textile use. In Ramie grass (Boehmeria nivea) the individual fibre reaches nearly nine inches long, in the Stinging Nettle (Urtica dioica), three inches. Stinging hairs are often present on the stem and leaves. CystoHths are commonly present in much enlarged epidermal cells, and vary in form and frequency in different species or groups of species (fig. 13). They are more or less evident in the dried leaf as punctiform or elongated Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Rendle, A. B. (Alfred Barton), 1865-1938. Cambridge, University press
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