640 EXPERIMENT STATION RECORD. 



where the effect protluced is not great, grass may be beneficial from a com- 

 mercial point of view in promoting fruitfulness and by increasing the color of 

 the fruit. The proportion of roots extending into the grassed ground, although 

 sufficient to make the grass effect apparent, was remarkably small, in some 

 cases amounting to only 1/2000 of the weight of the whole tree. 



A test of 6 different kinds of forest trees indicates that they are affected by 

 grass in the same way as fruit trees, when the grass is sown immediately after 

 planting. Conifers planted in light soil suffered less than other trees and 

 some recovery occurred with them as time went on. Of 18 different grasses 

 grown under apple trees the deleterious action was greater with the strong- 

 growing grasses than with the weaker ones. Clovers had a similar stunting 

 effect but the color of the leaves was not impaired as with trees growing in 

 grass. 



In their search in various directions for the cause of the grass effect the 

 authors have been unable to trace tbe injurious effect of the grass to the vari- 

 ation in depth of good soil available for root development; to interference 

 with soil aeration, soil temperature, and soil moisture ; to its influence on food 

 supply ; or to a physical alteration in the soil. Experiments in which the soil 

 was made alkaline indicated tbat the grass effect could not be attributed to 

 alkalinity produced by the grass in its growth. The bacterial condition of 

 grassed and tilled soils was also partially investigated without revealing any 

 positive relation between the grass effect and either beneficial or harmful soil 

 bacteria. See also a previous note (E. S. R., 20, p. 737). Likewise the general 

 behavior of grassed and tilled soils toward germinating seeds of various kinds 

 gave no direct evidence in favor of a toxic substance in grassed soils. 



Finally, in some pot experiments with trees, the authors found that when 

 trays containing grass growing in sand were placed on the surface of the soil 

 or sand in which the trees were growing so that the leachings from the grass 

 reached the tree roots witb practically no exposure to the air, the leachings 

 had a very deleterious effect. When the grass leachings were exposed to the 

 air, however, they had a beneficial effect on tree growth. From this evidence 

 the authors conclude that a toxic substance is formed by growing grass, which 

 substance is readily oxidized into some substance which favors plant growth. 

 This explanation, it is pointed out, is in full accordance with what has been 

 established as to the behavior of heated soils toward plants (E. S. R., 24, 

 p. 421). 



The appendix of this report contains reprints of papers by S. IT. Pickering on 

 Studies of the Changes Occurring in Heated Soils (E. S. R.. 24, pp. 301, 420) 

 and Plant-Growth in Heated Soils (E. S. R., 24, p. 421). Some additional work 

 on the germination of seeds in heated soils, here reported, confirms the previous 

 conclusion that there is a continuous increase in the toxic effect from the lowest 

 temperatures of heating upwards. The appendix concludes with a discussion 

 of Experimental Error in Horticultural Work, by the above author.'^ 



Agrologic conditions in relation to asparagus culture (8ta. Agron. Aisne 

 Bill., 1911, PI). 79-85). — This comprises a brief survey of soil conditions, in- 

 cluding analyses of soils from the asparagus region in the vicinity of Laon, 

 France. 



Tomatoes. — I, Varieties, culture, and canning, H. P. Stuckey and J. C. 

 Temple (Georgia 8ta. Bui. 96, pp. 37-68, figs. 7). — This consists of a collection of 

 notes on varietal, cultural, and canning experiments with tomatoes, conducted 

 at the Georgia Station principally during the past 8 seasons. Introductory 

 considerations deal with the classification and history of the tomato, construc- 



« Jour. Bd. Agr. [London], 1911, Nov., Sup. 7, pp. 38-47, 



