28 EXPEKIMENT STATION RECORD. [Vol.41 



3 : 100,000 calcium oxid solution. Antagonism was most complete when the 

 ratio sodium : calcium equaled 98 : 2. At this ratio the sodium was not ex- 

 cluded from the plant but was rendered harmless. The antagonism appears to 

 be internal rather than peripheral. 



The influence of the roots of growing plants upon the activity of soil micro- 

 organisms as indicated by the production of carbon dioxid from the soil, 

 J. R. Neller {New Jersey Stas. Rpt. 1911, pp. Jillf, 415). — The possil)le influence 

 of the roots of growins? plants on the rate of liberation of plant food by soil 

 microorganisms has been investigated by growing buckwheat and barley plants 

 in soil or sand under bell jars and noting the production of carbon dioxid which 

 was derived from decomposing organic matter. In the case of the plants grown 

 in sand, ground alfalfa hay was added as a source of carbon dioxid. 



It was foiind that slightly more carbon dioxid was liberated from the bell 

 jars containing plants than from those without plant growth. In a second 

 series of experiments buckwheat was grown as a residual crop in the same jars 

 of sand, and again more carbon dioxid was recovered from the bell jars con- 

 taining plants than from the others. 



The author concludes tliat under the conditions of the experiments the grow- 

 ing roots of barley and buckwheat do not inhibit the decay of organic matter. 



Gas interchange in Mesembryanthemum and other succulents, H. M. Rich- 

 ards {Carnegie Inst. Waslthif/ton Year Book, 11 {1918), pp. 63, 6/f). — A con- 

 tinuation of work previously reported (E. S. R., 40, p. 29), the problem now 

 being to account for the low carbon dioxid: oxygen ratio. It is suggested that 

 occlusion of carbon dioxid by the fleshy tissue may be involved. It is considered 

 probable that the processes involved are somewhat different from those pre- 

 sented by the succulent tissue of the cacti. It appears to be important to select 

 tissues of like acidity in order to obtain proper results from such work. 



Photosynthesis and respiration, H. A. Spoehr and F. Long {Carnegie lust. 

 Washington Year Book, 11 {1918), pp. 60, 61). — It is stated that for the purpose 

 of moi'e adequate study of photosyntliesis, for which purpose simple, thin leaves 

 have proved to be the best material, a rather elaborate device has been con- 

 structed for accurate control of temperature, light, air supply, and Vi'ater vapor. 

 The method now used is based upon the differential determination of the 

 amount of carbon dioxid fixed by the plant, as determined with special appa- 

 ratus for estimating the carbon dioxid absorbed in barium hydroxid. The 

 features of the general problem now under investigation are rather numerous, 

 though closely coordinated and interdependent, comprising a study of the basic 

 metabolism of mature leaves and the influence of such metabolism and of the 

 varying sugar content of the leaf on photosynthesis. 



It is stated that leaves of different species give enormous differences as 

 regards rate of carboliydrate elaboration and consumption. In cacti and other 

 plants rich in carbohydrates, increase thereof above certain limits does not 

 result in increased carbon dioxid evolution. Photosynthesis appears to be 

 closely related to sugar content and to the respiratory activity of the leaf. 

 Leaves having carbohydrate supply greatly depleted show, when first exposed 

 to light, a low rate of carbon dioxid fixation. This rises until an abundance of 

 carbohydrates lias accumulated, after which it decreases. 



The carbohydrate economy of cacti, H. A. Spoehr {Canwgie Inst. Washing- 

 ton Year Book, 11 {1918), pp. 61-63). — Having followed this subject through 

 the third year (E. S. R., 40, p. 30), the author i-oports that the continued 

 dry woatluu' kept the monosaccharid content low until the cold nights of the 

 late winter months (effected a change, the monosaccharids then rising and the 

 carbohydrate' equilibrium becoming about normal after the occurrence of the 

 late winter rains. 



