. The ecological relations of roots . here it forces its waythrough the crevices of the semi-decomposed rock. The number of largerbranches is few, usually not exceeding 2 or 3. One plant gave off only onelarge branch, about 2 man. in diameter, at a depth of 3 inches. As is charac-teristic of numerous other plants examined, this lateral branched freely andran off in a direction nearly parallel with the surface for about 15 to 20inches, ending in a network of well-branched rootlets. On another plant alateral ran off more than 36 inches from the base of the stem, branching againand again. Other s
. The ecological relations of roots . here it forces its waythrough the crevices of the semi-decomposed rock. The number of largerbranches is few, usually not exceeding 2 or 3. One plant gave off only onelarge branch, about 2 man. in diameter, at a depth of 3 inches. As is charac-teristic of numerous other plants examined, this lateral branched freely andran off in a direction nearly parallel with the surface for about 15 to 20inches, ending in a network of well-branched rootlets. On another plant alateral ran off more than 36 inches from the base of the stem, branching againand again. Other smaller branches arise from the tap in great are only a few centimeters long, but well-branched and densely coveredwith root hairs. The older cortex is black and of a papery texture, peeling offreadily. Paronychia jamesii.—This small, cespitose perennial forms a consocies ofthe community. It has a tap-root about 5 mm. in diameter. Like all otherplants on the gravel-shde, the top has been pushed down the slope several. Fig. 32.—Paronychia jamesii. inches. The tap breaks up into several larger laterals, usually 3 to 5, and agreat number of smaller ones. Some of the laterals run off in a horizontaldirection to a distance of 30 inches or more, at about 2 to 4 inches in depth,branching repeatedly, as shown in figures 32 and 33, and being abimdantly THE GRAVEL-SLIDE COMMUNITY. 83 supplied with minute, absorbing rootlets. Others run off obliquely, whilestill others parallel more or less the attenuated tap-root, and like the tap areabimdantly suppHed with both long and short rootlets, the whole forming awonderfully efficient absorbing system. Compared with the transpiring sur-face, the root system is very well developed. The surface view in the figureshows the roots at a depth of 2 to inches. The dotted lines show wherethey turn downward. No roots were found to penetrate to a greater depththan 30 inches. Aletes acaulis.—This low umbellif-erous plant, which is o
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Keywords: ., bookcentury1900, bookdecade1910, bookidecologicalre, bookyear1919
