. The ecological relations of roots . ree last species as compared with the deeper-root habit of Agropyrum and certain dicotyledonous plants is shown graph-ically in figures 6 and 7. THE ROOT SYSTEMS OF OTHER PRAIRIE SPECIES. Since the root systems of 21 of the most important non-grassyprairie species have been described in detail in a former publication(1915), it will be necessary here only to present a summary statement,so that it may be possible to compare their root systems directly withthe plants of the eastern prairies and later with those of the a comparison will help us to
. The ecological relations of roots . ree last species as compared with the deeper-root habit of Agropyrum and certain dicotyledonous plants is shown graph-ically in figures 6 and 7. THE ROOT SYSTEMS OF OTHER PRAIRIE SPECIES. Since the root systems of 21 of the most important non-grassyprairie species have been described in detail in a former publication(1915), it will be necessary here only to present a summary statement,so that it may be possible to compare their root systems directly withthe plants of the eastern prairies and later with those of the a comparison will help us to more clearly evaluate the responseto the conditions under which the several plant communities grow. Lupinus ornatus.—This plant and L. leucophyllus are the two species oflupines most widely distributed on the high prairies of eastern form extensive summer societies, the former on the drier slopes andridges, the latter on moist hillsides and in the valleys. Several of the 24 root 34 THE ECOLOGICAL RELATIONS OF THE PRAIRIES OF THE PACIFIC NORTHWEST. 35 systems examined reached depths of over 10 feet; because of the deviouscourse they pursue, the tap is frequently much longer. Indeed, one wasfound to have a length of nearly 13 feet. The abundant laterals, their widespread, and the clusters of terminal branches, together with the root nodules,are shown in figure 7. Lupinus leucophyllus.—This lupine has a much larger transpiring surfacebut a much smaller absorbing surface than L. ornatus, which it resembles inhaving a well-developed tap-root, usually with several laterals, all of whichare branched to the third and fom^th order. However, the root system ismuch less extensive than that of L. ornatus; its average depth is only about 5feet (fig. 7). Astragalus arrectus.—This legume forms marked estival societies, theplants drjdng up during the first week in July. It has a strongly developedtap-root, which usually pursues a com^e directly downward and sends
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