Text-book of botany, morphological and physiological . roots undergo a subsequent increase in thickness, and serveas store-houses, as in many Dicotyledonsand Monocotyledons, that the original fili-form shape is changed into the fusiformor into tuberous swellings (as in turnips,tuberous roots of Dahlia, Bryonia, Aspho-delus, &c.). Roots rarely form chlorophyll {e. Menyanthes), and even then only insmall quantities ; usually they are quitecolourless, not only when^they grow in theground, but also in water or air. A subsequent basal growth appearsnever to occur in roots as it does in manylea
Text-book of botany, morphological and physiological . roots undergo a subsequent increase in thickness, and serveas store-houses, as in many Dicotyledonsand Monocotyledons, that the original fili-form shape is changed into the fusiformor into tuberous swellings (as in turnips,tuberous roots of Dahlia, Bryonia, Aspho-delus, &c.). Roots rarely form chlorophyll {e. Menyanthes), and even then only insmall quantities ; usually they are quitecolourless, not only when^they grow in theground, but also in water or air. A subsequent basal growth appearsnever to occur in roots as it does in manyleaves and internodes when once the re-gions near the apex have been transformedinto permanent tissue. Interstitial growthbehind the apex often continues, however,for a long time (in Lycopodiacese accord-ing to NageU and Leitgeb). The extension of the tissue commences immediately behind the terminal part of the root which has been formed of primary meristem—an arrangement by which the elongation of the roots in the ground is essentially Fig. 114.—I^ongitudinal section of the grain of Zea Mais(X about 6); c pericarp; ?t remains of the stigma; fs base ofthe grain ; <^ hard yellowish part of the endosperm ; e7Li whiterless dense part of the endosperm ; jcscutelluin of the embrjO ;jj its point; e its epidermis ; k plumule ; iv (below) the primaryroot; 7US its root-sheath ; lu (above) secondary roots springingfrom the first internode of the embryo-stem it. (a) The primary root of the embryo of most Phanerogams gives the impression ofbeing entirely superficial, as if its apex were the actual posterior termination of theembryonal stem ; but its first origin is endogenous ; for the posterior termination of theembryo is connected with the pro-embryo in Phanerogams, and the primary root is, atits first origin, covered by this. (A more exact account of this, according to the mostrecent researches of Hanstein on the formation of the embryo will be given in Book II,on the Cha
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Keywords: ., bookcentury1800, bookdecade1870, booksubjectbotany, bookyear1875
