THE CHAPARRAL COMMUNITY. 



27 



Corylus americana. — This shrub does not get so far into the prairies from 

 the bordering eastern forests where it forms a layer as do the preceding, and 

 in this respect shows its less xerophytic habit. But in many situations, from 

 Minnesota to Kansas, thickets of Corylus come into direct competition with 

 prairie vegetation. 



Corylus spreads by means of large woody underground parts, as shown in 

 plate 15, c. These run at a distance of only 4 to 6 inches under the surface 

 and give rise at intervals to numerous erect shoots from 2 to 7 feet high and 

 also to multitudinous roots, some of which are more than 1.5 cm. in diameter. 

 Some of the smaller roots run vertically toward the surface and branch pro- 

 fusely into very fine ultimate branchlets, for Corylus, Uke the preceding 

 shrubs, is a strong competitor of the grasses for moisture in the surface soil. 

 Indeed, the surface foot or two of soil is well filled with absorbing rootlets, the 

 longer roots being only fairly well supplied with laterals to a depth of 10 or 11 

 feet. These larger roots, as shown in plate 15, a, either pursue a rather verti- 

 cally downward course, or extend obhquely for a distance of 1 or 2 feet or 

 more and then turn downward. Roots were traced to depths of 10, 10.5, and 

 11.5 feet respectively. They are dark brown in color, very woody, with a very 

 thin cortex, and frequently branch rather dichotomously, although the 

 branches are seldom equal in size. The branches are often very coarse and 

 sometimes run in parallel groups several inches without giving rise to absorb- 

 ing rootlets. The main root-ends are not very well supphed with fine branches. 

 Thus it may be seen that while Corylus penetrates to greater depths than 

 Rhv^ or SymphoricarpoSy its absorbing system is hardly developed to such a 

 high degree. 



Vitis vulpina. — At a depth of over 10 feet in the Rhus thicket a root of 

 Vitis was encountered. It was 18 mm. in diameter and ran horizontally 

 across the trench. It gave off numerous branches, some of which reached 

 depths of 12 feet. Its branching is not unhke that of the larger roots of the 

 hazel. In the Corylus thicket, roots of grape were traced to depths of 13 feet 

 3 inches and 13 feet 6 inches respectively. The diameter of roots near the 

 surface was about 1 cm. ; at 10 feet it was 2 and 3 mm. respectively. Another 

 underground part ran horizontally at a depth of 2 feet for a distance of more 

 than 6 to 8 feet. Such an enormous absorbing area as is possessed by Vitis 

 gives us the clue to its ability to have a leaf area not unlike that of many trees 

 and yet be able to five often in apparently rather dry situations. 



Rosa arkansana. — This shrub is widely distributed throughout the scrub 

 and prairie areas. Although usuallj^ held in check in the dense grassland sod, 

 except where local disturbances have favored its development, in the sub- 

 climax grassland it frequently forms dense brush over the less-exposed slopes. 

 In the sandhills westward it again assumes an important role, areas several 

 acres in extent frequently being controlled by this species. 



As shown in plate 16, a, this plant propagates by rhizomes. This parent 

 plant had given rise to 5 distinct clumps of stems, the youngest of which was 

 5 years old and more than 5 feet from the oldest. Fragments of other hori- 

 zontal parts, which had not yet developed shoots, may be seen. It may also 

 be noticed that the plant next to the parent is the only one that has developed 

 a tap-root of its own. Indeed, the other roots arising from the horizontal 

 portion ran obhquely upward, rather horizontally or, at most, only very 

 obliquely downward, and none reached any considerable depth when com- 

 pared with the taps from the older plants. The tap-root from the second 

 plant reached a depth of 15 feet 2 inches; the main tap pursued a nearly ver- 

 tically downward course to a depth of 21 feet 2 inches. 



