. The natural history of plants, their forms, growth, reproduction, and distribution;. Botany. ANGIOSPERM^, DICOTYLEDONES. 749' The Centrospermee are extremely rich in inorganic salts, and in the case o£ many of the species soda is extracted from the ash obtained by burning the plants. The Piperace^ contain aromatic and pungent substances; the Urticaceee secrete enzymes in their stmgmg-hairs (see vol. i. p. 441). The leaves are lobed in Urticaceae and Ohenopodiacese, in the rest they are undivided and have entire margins. In several Cheno- podiacesB the cauline leaves are squamiform, and assim
. The natural history of plants, their forms, growth, reproduction, and distribution;. Botany. ANGIOSPERM^, DICOTYLEDONES. 749' The Centrospermee are extremely rich in inorganic salts, and in the case o£ many of the species soda is extracted from the ash obtained by burning the plants. The Piperace^ contain aromatic and pungent substances; the Urticaceee secrete enzymes in their stmgmg-hairs (see vol. i. p. 441). The leaves are lobed in Urticaceae and Ohenopodiacese, in the rest they are undivided and have entire margins. In several Cheno- podiacesB the cauline leaves are squamiform, and assimilation is then effected by the green cortex of the branches, which are trans- formed into phylloclades. The Piperacese are distinguished by a peculiar distribution of the bundles in the foliage-leaves. The lateral strands do not branch' off from the midrib in the usual way, but are appressed to it and can be traced to the base of' the lamina. The Urticace^ also, particularly the genus Parie- taria, exhibit a peculiar disposi- tion of the bundles (see vol. i. p. 629). The Chenopodiace^ are destitute of stipules, the Paronychiaceae have large mem- branous stipules which protect the foliage-leaves, the Poly- gonacese are distinguished by curious sheathing stipules. In the Caryophyllaceas and some Paronychiaceae the floral enve- lopes are differentiated into calyx and corolla; in Nyctagin- acese, Amaranthacese, and most Polygonacese there is a petaloid perianth, whilst in Chenopodi- acese and Urticaceae there is a sepaloid perianth. The perianth in Nyctaginaceae resembles a corolla most strongly when the bracts are connate and form a sepaloid envelope or involucre, as is the case, for instance, in the Marvel of Peru (Mirabilis Jalapa, see fig. 425). The lowest portion of the perianth in Nyctaginaceae continues to grow after the flower has faded and forms a leathery or woody investment to the fruit (see fig. 425 ^).. In several Chenopodiaceae and;. Fig. 425.—Nyctaginacese, Mirab
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectbotany, bookyear1895
