ECADS. 87 



To summarize the data from the six widely separated stations in the three 

 grassland associations: Psoralea has a deep tap-root with no provision for 

 surface absorption, and in fact seldom branches in the surface foot of soil. 

 The laterals are often large and wide spreading as well as deeply penetrating. 

 The root system as a whole is not well supplied with fine absorbing rootlets. 

 This is a stable species, little modified in root habit by varying conditions of 

 the environment. Its presence is indicative of available moisture in the 

 deeper soil. 



Artemisia frigida. — This low, semi-woody perennial is especially well de- 

 veloped in the short-grass plains and mixed prairie. It frequently forms ex- 

 tensive socies when the natural vegetation is greatly disturbed, or in rocky 

 or gravelly situations, especially near the mountains. It has been thoroughly 

 examined at Colorado Springs. Arising from the base of the clustered woody 

 stems, the strong tap-root descends vertically downward for a distance of 4 to 6 

 feet. Just below the soil surface many laterals originate. These run off either 

 parallel with the soil surface or only rather obliquely with it for distances of 

 8 to 12 inches or more before turning rather abruptly downward. The 

 smaller roots branch profusely and furnish the plant with an excellent absorb- 

 ing system in the surface soil. Many of the well-branched laterals reach 

 depths of 2 or 3 feet or more and are not infrequently as large in diameter as 

 the tap-root. 



In the dark sandy loam of the mixed prairie at Limon, roots of this plant 

 were traced to a depth of from 3.7 to 3.9 feet. The root habit in every respect 

 agreed with that at Colorado Springs. At Ardmore, the plant was found 

 growing in Pierre clay underlaid at a depth of 4 feet with a very hard layer of 

 gravel and sand, below which was a stiff sandy loam. Many of the roots 

 ended with well-branched termini in the layer of gravel, although some pene- 

 trated even deeper. The general root habit, including the widely spread surface 

 laterals, was characteristic, as was also the amount of brandling in the clay, 

 but the degree of branching of the roots in the gravel and sand was much 

 more pronounced than usual. 



Chrysopsis villosa. — This is a very widely distributed composite, which 

 forms extensive societies both on the hard land and in the sandhills. Several 

 specimens were examined in the mixed prairie at Limon. All had strong tap- 

 roots which were woody to a depth of 1 or 2 feet. The diameters of these 

 varied from 8 to 12 mm. Their course was almost vertically downward. 

 The first 1.3 feet of the tap was abundantly supplied with small laterals, 

 which ran out in a direction parallel with the soil surface for a distance of 

 0.2 to 1.5 feet. While many of the laterals are mere threads, others are 2 mm. 

 thick. All are practically destitute of branches. Other laterals, usually not 

 over 1.5 mm. in diameter, occur at various depths, but these are not at all 

 numerous, and while they may run off horizontally or obliquely 1 or 2 feet from 

 a vertical line with the tap-root, they are scarcely at all rebranched or provided 

 with smaller absorbing rootlets. The absorbing system in the surface soil 

 stands out strikingly and is characteristic of many species of dry grassland. 

 The maximum depth of some of the smaller plants was about 5 feet, although 

 others reached depths greater than that of any of the trenches (7 feet). 

 With two exceptions the root habit was similar to that previously described 

 in the hard loam soil at Colorado Springs (Weaver, 1919:117-119). The 

 course of the tap-root was much straighter and not curved and kinked through 

 distances of 1 or 2 inches of the fairly mellow sandy loam. Moreover, the root- 

 tips and some of the laterals were branched to a greater degree, but as a whole 

 the root system resembles closely that found in hard soil and is quite different 



