. The ecological relations of roots . f shorter, minutely branched,often vertically descending rootlets. Thus the plant is provided with an 94 THE ECOLOGICAL RELATIONS OF ROOTS. effective absorbing system, which ramifies widely and fills the soil from adepth of from 4 to 36 inches. The whole root system is characteristic of thehalf-gravel-sHde root habit. Besseya plantaginea.âThis plant frequently grows in clusters of 3 or more,the individuals of which are connected by short rhizomes about 5 mm. or lessin diameter and 2 or 3 inches long. The base of the plant and these rhizomesare densely cove
. The ecological relations of roots . f shorter, minutely branched,often vertically descending rootlets. Thus the plant is provided with an 94 THE ECOLOGICAL RELATIONS OF ROOTS. effective absorbing system, which ramifies widely and fills the soil from adepth of from 4 to 36 inches. The whole root system is characteristic of thehalf-gravel-sHde root habit. Besseya plantaginea.âThis plant frequently grows in clusters of 3 or more,the individuals of which are connected by short rhizomes about 5 mm. or lessin diameter and 2 or 3 inches long. The base of the plant and these rhizomesare densely covered with fleshy roots about 2 mm. in diameter. As many as30 to 40 of these roots occur on a single inch of the rhizome. Many of thempursue a vertically downward course and end at a maximum depth of from25 to 30 inches (fig. 39). Others run out rather parallel with the surfaceof the soil and at a depth of 2 or more inches to a distance of over a foot, whenthey turn abruptly downward, reaching a depth of 16 or 18 inches. Still others. Fig. 39.âBesseya plantaginea, showing the widely spreading root system. fill in the angle between the horizontal and vertical roots, running off obfiquelyand then turning downward. Very few branches occur on the first 4 to 6inches of the root. But beyond this point the roots (which are now a milH-meter or less in diameter) branch freely, sending off laterals to a distance of5 or 6 inches, the last 12 to 18 inches being so well branched and rebranchedas to form a fine absorbing network. Thus the soil within a radius of at leasta foot from the plant and at a depth of from 20 to 30 inches (except the sur-face 2 inches) is rather completely filled with absorbing rootlets of this fleshyperennial. As its root system shows, Besseya is an excellent illustration of a THE HALF-GRA\^L-SLIDE COMMUNITY. 95 transitional form between the gravel-slide type and that of ordinary roots are dark tan in color and are fairly tough and resistant. Fiveplants wer
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