. A textbook of botany for colleges and universities ... Botany. STEMS 673 ground, rooting copiously at the fre- quent nodes (fig. 712). Also to be classed with runners are such stems as those of Decodon and Rubus which bend over and take root if the tip comes into contact with moist soil. Prostrate stems differ from runners in not taking root, though stems classed as prostrate {Arctostaphylos, Juniperus horizontalis, fig. 984) fre- quently develop roots under favor- able conditions. When the stems of Decodon or Rubus bend over and root at the tip, probably it is because there is not sufficien
. A textbook of botany for colleges and universities ... Botany. STEMS 673 ground, rooting copiously at the fre- quent nodes (fig. 712). Also to be classed with runners are such stems as those of Decodon and Rubus which bend over and take root if the tip comes into contact with moist soil. Prostrate stems differ from runners in not taking root, though stems classed as prostrate {Arctostaphylos, Juniperus horizontalis, fig. 984) fre- quently develop roots under favor- able conditions. When the stems of Decodon or Rubus bend over and root at the tip, probably it is because there is not sufficient mechanical tissue to hold the stems erect. Pos- sibly the same is true of many runners, since they often appear phophototropic at the outset. In any case, the development of ad- ventitious roots is likely thenceforth to cause a downward pull on the older parts of the runner. Ne- phrolepis is somewhat unique in possessing both rhizomes and run- ners; the rhizomes develop first and give rise freely to adventitious roots. The runners are peculiar leafless organs without a conspicuous r61e; if they are removed, some of the rhizomes develop into aerial shoots. The advantages of runners.—Run- ners compare favorably with rhi- zomes as organs of vegetative re- production, as may be seen in the development of a colony of straw- berries or of white clover. They commonly elongate more than do. Figs. 985-988. —Salureja glabra: 985. the basal portion of a plant, showing a runner (s) in which all of the leaves appear to issue from the upper side, because of stem twisting and petiole curvature; at the nodes adventitious roots (r) issue from the under side of the runner, fastening it to the ground; note the unfastened ascending tip {t); if the runner is severed at a. a', or a'\ the rooted portions develop into in- dependent plants; 986, a short, broad leaf, characteristic of a runner, developed especially in the autumn, and remain- ing over winter; 987, an elongated, nar- row leaf, chara
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectbotany, bookyear1910
