AGRICULTITEAL BOTAKY. 523 



The cofficients of correlation were rather small, but they were in every Instance 

 positive, indicating that the selection of larger seeds will give a somewhat 

 higher yield of pods. 



Weeds in relation to soils — Norfolk, Winifred E. Beenchley (Jour. Bd. 

 Agr. [London], 20 (1913), No. 3, pp. 198-205) .—In continuation of a series of 

 papers (E. S. R., 29, p. 30), the author reports the results of an investigation 

 conducted on soil of Norfolk to determine the relation of weeds to different 

 types of soil. 



The effect of some Puget Sound hog waters on the root hairs of Tradescan- 

 tia, G. B. RiGG (Bat. Gas., 55 (1913), No. 4, pp. 31. ',-32 6). —The author ad- 

 vances the theory that plants other than bog xerophytes are excluded from peat 

 bogs because of their inability to produce normal root hairs in the toxic habitat 

 of bogs. 



The experiments show that Tradescantia produces stimted root hairs when 

 grown in bog water, as compared to normal root hairs in water from open 

 lakes or springs immediately adjacent to bogs. When grown in water from 

 drained or partially drained bogs the plants produced almost normal root hairs. 

 The stunting of the root hairs by bog water is comparable with that due to 

 dilute solutions of sea water, formalin, tannic acid, gelatin, coffee, and tea. 

 When bog water was diluted with an equal volume of tap water, or in some 

 cases with one-half its volume of tap water, the stunting effect on the root 

 hairs disappeared. The stunting effect may be increased by boiling the water 

 down to a fraction of its original volume. Many typical bog plants are said 

 to have no root hairs, and there is believed to be a toxin or toxins in bog 

 water the effect of which disappears with drainage of the bog. 



The relation of environmental conditions to the phenomenon of perma- 

 nent wilting in plants, J. S. Caldwell (Physiol. Researches, 1 (1913), No. 1, 

 pp. 1-56, figs. S; Prelim. Abs., pp. ^).— From the study of Phaseolus vulgaris, 

 Xanthium commune, Marlynia louisiana, and Physalis angulata UnJciana in 

 midsummer conditions in southern Arizona, the author reached the following 

 conclusion : 



"Permanent wilting appears to be a condition of general plasmolysis (but not 

 of death) in all the tissues of the plant, with accompanying cessation of certain 

 of the protoplasmic activities. This condition is characterized by a water con- 

 tent of the functioning foliage which is nearly constant for any species. The 

 reduction of the water content to this point is the resultant of the action of 

 transpiration versus root absorption ; if aerial conditions permit these two 

 processes to go on at approximately equal and moderate rates until the water 

 supply fails at its source, there remains in the soil a quantity definitely related 

 to the physical constants of the soil. . . . This excess of soil water is only 

 effective temporarily to preserve the life of the root hairs; its amount is more 

 or less definitely related to the aerial conditions prevailing throughout the 

 period of wilting and rises with increase in the transpiration rate. Thus the 

 only constant with which we have to deal in cases of wilting under widely 

 varying conditions is a physiological constant, a condition of the plant 

 protoplasm with respect to water, which arises as a result of the Interaction 

 upon the plant of a complex of external conditions, of which the soil moisture 

 content is only one. The soil moisture content at permanent wilting is there- 

 fore a variable which increases with change in the value of the other terms of 

 the equation, especially with increase in the evaporating power of the air be- 

 yond a certain limit ; and it is not to be considered as independent of these 

 other terms." 



A bibliography of the subject is appended. 



16385°— No. 6—13 3 



