222 EXPERIMENT STATION RECORD. [Vol.38 



tomato, 2 variotirs of clover, and IG varieties of grass. In no case have negative 

 results'beon obtained, though the degree of injury varied greatly, this variation 

 being ascribed mainly to the condition (vigor) of the plants employed. The 

 reduction of growth due to tins treatment varied from 6 to 97 per cent. 



Tests employing the method of exclusion narrowed down the possible causa- 

 tion of injury to trees by grass to the possible formation of some deleterious 

 substance by the growing grass, the effect being strongly suggestive of a toxin. 

 Exposure of the leachings to the air for 24 hours removed the toxic property. 

 A 2-in. layer of pumice stone acted in the same beneficial manner. The effect 

 of a plant on its own kind is apparently greater than on a plant of another 

 kind. A stronger plant not only keeps ahead of a weaker or younger one, 

 but an older plant usually gains on a younger one continually. 



Fungus fairy ring's in eastern Colorado and their effect on vegetation, 

 H. L. Shantz and R. L. Tiemeisel (U. S. Dept. Agr., Jour. Agr. Research, 11 

 (Idll), No. 5, pp. 191-246, pis. 21, figs. 15).— This paper deals with fairy rings 

 caused by fleshy fungi, the studies on which won^ made on the high plains at 

 Akron, Colo., during the period from 1907 to 1916, inclusive. The fairy rings 

 are distinguished as those in which the vegetation is killed or badly damaged, 

 caused by Agnriciis tabularis; those in which the vegetation is only stimulated, 

 caused usually by species of Calvatia, Catastoma, Lycoperdon, Marasmius, etc. ; 

 and those in which no effect can be noted on the native vegetation, caused by 

 Lepiota spp. 



The authors report that fairy rings start from the point of germination of the 

 fungus spores and spread outward at approximately an equal rate in all direc- 

 tions. Growth is continuous until some obstacle is met with, which may be 

 passed around in case of ant hills, but growth is terminated where two rings 

 come in contact. As the fungus filaments spread outward they are said to con- 

 sume a portion of the organic matter of the soil. The carbohydrates are con- 

 sumed, and the proteid portion is changed into amino acids and then into am- 

 monia. 



The effect of the fungus filaments on the soil is to reduce a part of the or- 

 ganic matter to ammonia, which is combined to form ammoniacal salts or is 

 converted by bacteria into nitrites and later into nitrates. When the mycelium 

 dies, it is reduced by bacterial action to ammonia, which may later be built up 

 into nitrates. The increase in available nitrogenous material in the soil occu- 

 pied by the young mycelium is said to stimulate the growth of the grasses or 

 other young plants, which consequently make greater demands on the soil 

 moisture. When this is exhausted, as in the case of A. tabularis, the mass of 

 fungus filaments prevents the penetration of rain water. The intense drought 

 to which the plants are thus subjected kills off the buffalo and grama grasses 

 and the other plants which may be associated with them, and the area is left 

 bare for the invasion of other plants. The mycelium after a few years dies, 

 leaving the soil still more enriched and no longer impervious to water. 



The stages in the succession on the bare areas are an early weed stage, fol- 

 lowed by a late weed stage, and this in turn by a short-lived grass stage, which 

 is succeeded by a perennial stage, and this finally gives way to the original 

 short grass cover. 



Growing alien cacti in Michigan, W. E. Praeger {Rpt. Mich. Acad. Sci., 11 

 {1915), pp. 156-158). — Thirteen species of cacti, representing four genera, 

 from various altitudes in Arizona were tested iu Michigan with the result that 

 all died out in four winters. The general conclusion is that Arizona cacti can 

 not survive Michigan winters, the warm, wet autumn weather probably being 

 important in this connection. Cacti native to this region show a gradual loss 

 of turgidity in the fall, which is thought to serve as the equivalent of a 



