580 Physiologie. 



change in the quantitative relations between the loss in dry \Yeight 

 of the cultures and the CO, of respiration. Hence formaldeh^'-de was 

 not converted into COo by the plants, nor used as a source of food 

 material in the dark. Probablj^, therefore, formaldehyde may 

 function as a stage in photosynthesis, but the production from it 

 of sugars and other food materials requires light energy. This 

 conclusion is in contradiction to most chemical theories on the sub- 

 ject; but the results tend to confirm such a hypothesis as that of 

 Collie, which postulates the production from formaldehyde of a still 

 more unstable substance, keten (CHz=CO), before it is further 

 elaborated into food materials. F. Cavers. 



Carputhers, W., On the vitality offarm seeds. (Journ. Roy. 

 Agric. Soc. LXXII. p. 168-183. 1911.) 



Samples of thirty five different kinds of seeds were kept from 

 the harvest of 1895, and their germinating capacity was tested year 

 after j'^ear. With wheat and barley a serious decrease in the per- 

 centage of germinating seeds occurs after five 3''ears, while oats 

 retain their vitality tili after the ninth year. The grasses fall into 

 three groups: 1) Those which retain their vitality for about four 

 years, and then lose ground rapidly {Phloeiini pratense)\ 2) Those 

 in which the germinating capacity drops rapidly from the first to 

 a point below 10^/q, and then remains stationary for a time {Festtica 

 ovina)\ 3) Those which lose vitality steadily from first to last [Loliian 

 italicwn). 



Leguminous plants show a similar Variation among themselves, 

 the true clovers losing littie during the first three or four 5'^ears, 

 then showing a rapid loss for another four years, the last IQO/o of 

 germinating power being very slowly lost during a further three 

 or four years. The reasons for this loss of vitality are discussed, 

 and curves and tables are given illustrating the results of the sixteen 

 years experiments. 



Other experiments seem to show that living embryos transfer- 

 red to the food Store of dead seeds utilise it freely, and that the 

 Store of food retains all its properties for many years after the seed 

 is dead. W. E. Brenchley. 



Crump, W. B., The Coefficient of Humidity: a new Method 

 of expressing the Seil Moisture. (New Phytologist. XII. p. 

 125—147. 1 textfig. 1913.) 



The author suggests a new method of expressing the soil moisture, 

 his "coefficient of soil humidity" being the ratio water-content|: humus- 

 content, and formulates the working theory that the humus as a 

 coUoid holds all, or practically all, the water in a humous soil, so 

 that even with relatively small humus-contents the water-holding 

 power of the non-colloid constituents may be neglected. Leaving 

 on one side the possibility that in other types of soil coUoid clay 

 may have a similar function, he discusses the question how far the 

 formula "the water-content is a function of the humus-content" 

 provides in the coefficient of humidity a satisfactory Instrument for 

 gauging the soil moisture of a plant habitat. Numerous tabulated 

 results are given for various types of soil, with mathematical reduc- 

 tion of these results to equations. The author's conclusions agree 

 with the results of the work of Briggs and McLane, though the 



