AGRICULTURAL BOTANY. 125 



It waf3 found that sr> per cent of the brands met their guaranties and that 

 the crude stock used in the fertilizers was generally of good quality. The aver- 

 age selling price was .$29.52, the average valuation $10.38. " A comparison of 

 analyses of brands for 5 years shows in some cases essential evenness and in 

 othei's considerable variation in comiiosition." The advantages and disadvan- 

 tages of l»uying mixed goods and separate ingredients are briefly stated and 

 the cooperative purchase of inimixcd fertilizing materials is recommended as 

 more economical. 



A general discussion of weather conditions and chemical composition, phys- 

 ical characteristics, biological content, irrigation, drainage, and tillage of 

 soils with reference to control of moisture and better utilization of fertilizers 

 are included in the bulletin. 



AGRICULTURAL BOTANY. 



The function of silica in the nutrition of cereals, I, A. D. Hall and C. G. T. 

 MoRisoN (Proc. Roy. Soc. [London], Her. B.. 11' (1906), No. B 520, pp. .'t5r)-.',ll, 

 fujs. 11). — A brief summary is presented of opinions relative to the function 

 of silica in plants. 



The authors call attention to the constant and considerable proportion of silica 

 in the ash of certain plants and give an account of held and pot experiments 

 to determine if possible its action. As a result of their investigations they 

 consider that silica, while not an essential constituent of plant food, plays an 

 important part in the nutrition of cereal plants, like barley. The effect of a 

 free supply of solnble silica shows itself in an increased and earlier formation 

 of grain, and it acts by causing an increased assimilation of phosphoric acid 

 i)y the plant. 



There appears to l)e no evidence that the silica within the plant causes a 

 more thorough assimilation of the phosphoric acid, or that in itself it promotes 

 the transfer of food materials from one part of the plant to the other. The 

 physiological function of silica are found to take place within the plant tissues, 

 and not in the soil as has sometimes been claimed. 



Utilization of the nitrogen of the air by plants, T. Jamieson {Agr. Re- 

 search Assoc. [.S'cof.] Rpf. liiii.'. pji. SI. pjx. 12). — The author rejects the 

 theory of Hellriegel and others that nitrogen assimilation in the higher plants 

 is confined to the Legnminosa^ and a few other orders of plants, where the 

 fixation takes place through the syml)iotic action of micro-organisms in the root 

 tubercles. 



He claims that nitrogen assimilation is a function common to many plants, 

 through the presence of specialized cells in the epidermis and also specialized 

 hairs on various aerial parts of the plant most abundant in the younger parts 

 of the plant. The basis of this theory seems to be albumin reactions observed 

 in certain thin-walled cells of the epidermis of the leaves and in certain 

 hairs, the author arguing that the formation of the albumin took place where 

 observed, and the absence of the reaction with iodin indicated the transfer 

 of the nitrogenous compounds from the specialized organs to the leaves for 

 the use of the plant. 



The action of radium on plants {Jnrdin. 20 {1906), 'So. .'i-il, p. Go). — The 

 influence of radium on seeds, it is stated, depends upon the thickness of the seed 

 envelop, its distance away from the radium, and the quantity of moist soil 

 covering it. When the moisture is excessive, germination may be retarded or 

 completely arrested. The transformations wliicli take place in the cellular tis- 

 sues are the same as those occasioned by too much light. Experiments made 

 with other radioactive substances, such as radiotellurium, have given similar 

 8989— No. 2—06 3 



