90 



Sir J. B. Lawes and Prof. J. H. Gilbert. [Jan. 9, 



The soil extracts, supposed to supply the organisms, were made by 

 shaking, in a large stoppered bottle, 1 part of the garden soil or lupin 

 sand with 5 parts of distilled water ; and after the heavier portions 

 had settled down, syphoning off the turbid liquid, which was then 

 passed through platinum gauze to separate any floating matter. The 

 liquid was again shaken before taking the quantity required for seed- 

 ing the soils, or for analysis. Determinations of nitric nitrogen by 

 Schloesing's method, and of total nitrogen by copper oxide, gave the 

 following results : — 





Per cent. 



In 25 c.c. extract. 



Nitric 

 nitrogen. 



Total 

 nitrogen. 



Nitric 

 nitrogen. 



Total 

 nitrogen. 



Garden soil extract .... 

 Lupin sand extract .... 



Per cent. 

 -000371 



-ooono 



Per cent. 

 003159 

 001184 



Milligram. 

 0-093 

 0-028 



Milligram. 

 0-790 

 0-296 



It is thus seen that the 25 c.c. of the garden soil extract used for 

 seeding contained little more than f of a milligram, and the 25 c.c. of 

 the lupin sand extract little more than | of a milligram of nitrogen ; 

 quantities which are quite immaterial considered as a supply of com- 

 bined nitrogen. 



The Seeds. 



The peas were of the description known as Maple field-peas. Four 

 lots, each of 100 seeds, weighed 27*554, 27*460, 27*218, and 27*506 

 grams; giving an average weight per seed of 0-274*3 gram. A large 

 number of single seeds was then weighed, and those only retained 

 for sowing or analysis which gave within 5 milligrams of the mean 

 weight. 



In the case of the blue lupins the largest and smallest seeds were 

 picked out and rejected. Of the remainder, four separate lots of 100 

 each weighed 19-2290, 19*9215, 18*7960, and 19*4580 grams, giving 

 an average weight per seed of 0*1935 gram. A large number of 

 single seeds was then weighed, and those only kept for use the weight 

 of which was within 5 milligrams of the average weight. 



From the yellow lupin seed the largest were removed by sifting, 

 and the smallest and those of a dark colour were picked out. Of the 

 remainder, three separate lots of 100 each weighed 12*1060, 11*9640, 

 and 11*6180 grams, giving an average weight per seed of 0*1190 gram. 

 From these, seeds were selected for use which weighed within 5 milli- 

 grams of the average weight. 



