HOBTICULTUEE. 139 



spraying with the solution to kill weeds. These results point to the probable 

 eflicieucj- of the formulas used as a weed destroyer. 



The plumber's blowlamp as a garden tool, H. K. Durham (Jour. Roy. Hort. 

 Soc. [London'], ffO {1914), Ko. 1, pp. 16-18). — This article describes a method 

 of using on a small scale the plumber's blowlamp to destroy weeds and sprout- 

 ing seeds at the surface of the ground. 



HORTICULTURE. 



Sap studies with horticultural plants, W. H. Chandler (Misssouri 8ta. 

 Research Bui. 14 (1914), pp. 491-552, figs. 13). — In connection with a study of 

 (he killing of plant tissue by low temiierature (E. S. R., 32, p. 42), freezing- 

 point determinations as well as electrical resistance and molecular weight 

 determinations were made of sap from the cortex of tissue of many different 

 kinds of plants, including orchard fruits as well as flowering plants and vege- 

 tables. The determinations were made throughout the winter season and during 

 part of the summer season with the view of detecting possible changes in the 

 sap during the winter that might help to account for the increased hardiness 

 of mature winter tissue. Although no changes were found that would explain 

 why plants acquire greater resistance to cold in winter, the data secured in 

 these investigations, as well as those from other sap studies, are here presented 

 for any value they may have in similar investigations. 



The data are presented in a series of tables and discussed under the follow- 

 ing general headings : Method of making freezing point determinations, deter- 

 mining the electrical resistance, molecular weight determination of plant sap 

 solute, plant density of various tissues of trees, sap concentration at different 

 periods of the year, sap concentration of green and ripe fruit, effect of vigorous 

 growth upon sap concentration, and sap concentration in relation to water 

 movement. A bibliography of related studies is given. 



The author's principal deductions from his studies as a whole are presented 

 in the following summary: "A very small proportion of the osmotic strength 

 of leaf and cortex sap as measured by the lowering of the freezing point is 

 produced by electrolytes, except in the leaves of succulent plants. It is also 

 true that generally more than half of the osmotic strength of leaf and cortex 

 sap is produced by neither sugars nor electrolytes. 



" The molecular weight of the sap solute varies for different tissues, but for 

 any given tissue it does not vary greatly except in early summer during the 

 period of rapid growth, when it seems to be somewhat smaller than at other 

 times. The molecular weight of the sap solute of twigs from peach trees 

 that have been forced into vigorous growth by pruning seems to be smaller 

 during most of the summer than that of the cortex sap of peach twigs from 

 trees not so pruned. 



" During the growing period there is a fairly constant increase in the 

 molecular concentration of the cortex sap from the roots up through the trunk 

 and large branches to the twigs, exceptions to this, apparently, being most com- 

 mon in the trunk. In late winter this greater molecular concentration of the 

 cortex sap in the upper portions of the tree does not generally prevail. The 

 molecular concentration of cortex sap is the smallest during the period of 

 rapid growth. In case of roots, especially, and to a lesser extent in other 

 tissues, the molecular concentration of the cortex sap is not so great during 

 early summer with trees that have been forced into vigorous growth by heavy 

 pruning as with trees not so pruned. 



"A molecular concentration as determined by the freezing point seems a fair 

 measure of the condition of nutrition, at least of the roots. The molecular 

 75575°— No. 2—15 1 



