Growth o/ Lemna minor in Mineral Culture Solutions. 485 



Table I. 



Series. 



Total solids added 

 (parts per million). 



Organic substance 

 (parts per million). 



■ 



Inorganic matter 

 (parts per million). 



II 



421 



368 



53 



Ill 



189 



97 



92 



IV 



44 



32 



12 



y 



17 



13 



4 



The greater quantity of inorganic matter in Series III than in Series II is 

 explained by the substitution of the inorganic chloride for the organic 

 hum ate radicle, and possibly also by a slight excess of calcium chloride used. 



An estimation of the mineral nutrients, nitrogen, phosphorus and potash, 

 was made only for Series II, as this series contained the maximum addition 

 of these nutrients. The figures obtained for these additions, as compared 

 with the quantities already present in Detmer's solution, are as follows : — 



Table II. 



* 



Amount of nutrient 

 present in Detmer 

 (parts per million). 



Amount of same 

 nutrient added 

 (parts per million). 



Percentage 

 of 



addition. 



Nitrogen (estimated as NH 3 ) 



Phosphorus (estimated as PjOs) ... 

 Potassium (estimated as K 2 0) ... 



393 

 204 

 1220 



19 -2 

 * 3 6 

 0-52 



4-8 

 1 -8 

 0-04 



Twenty plants of Zcmna minor, as nearly uniform as possible in size, 

 general healthiness and root development, were counted out into each of the 

 50 dishes. The solutions were changed twice each week in order to maintain, 

 as nearly as possible, the original balance of the salts, and to eliminate 

 bacterial contamination ; and, at each changing, the dishes were thoroughly 

 cleansed before the solutions were renewed. The plants in each dish were 

 counted every week. 



The plants in all the series multiplied fairly uniformly for the 1st week, 

 then the effect of the auximones in Series II and III became very marked, 

 until at the end of three weeks the plants in these series completely filled 

 their dishes. At this stage the plants in all 50 dishes were halved, one half 

 being retained, and the dry weight of the other half estimated. This was 

 repeated for a further three weeks, but at the end of the 7th week the 

 plants in Series II and III had become so numerous that they had to be 

 quartered, one-quarter only being retained instead of one-half. 



