FORMATION OF PROTEIDS ETC. 489 



experiments failed to prove any assimilation of nitrates in darkness, 

 but the consideration that the reduction of nitrates might require 

 larger quantities of sugar, led me to increase the latter from i 

 per cent, in the first experiments to 10 per cent, in my final experi- 

 ments. The results then turned out quite differently. 



I. EXPERIMENT WITH- ETIOLATED SHOOTS 

 OF BARLEY {Hordanu distichou.) 



Shoots of barley 15 cm. high, grown in the dark in moist saw 

 dust, were nourished with a 0.2% solution of sodium nitrate as well 

 as with other necessary mineral matters^" (from^ October 7 to 14) 

 until the shoots attained the average height of 28 cm., thus allowing 

 time to store up some of the nitrate. Hereupon, one portion of the 

 plants was dried and analyzed, while the other portion was care- 

 fully removed from the saw dust, well washed and put in a 10^ 

 solution of cane sugar half saturated with gypsum. On tlie fourth 

 day the plants were transferred to a solution of containing o.\% 

 mono- and di-potassium phosphate and as much of magnesium 

 sulphate. The plants were left in a perfectly dark room for 7 days, 

 during which time tlie temperature was Min. io°C. and Max. 20°C. 

 The solution was renewed every day ; no bacterial turbidity was 

 observed, the plants remained very healthy and grew 3-4 cm. On 

 October 21 the plants were taken out from the solution and dried 

 for analysis. The plants nourished with the nitrate until the 14, 

 contained a moderate quantity of nitrates, as shown by the 

 diphenylamine reaction. But the i:)lants further kept in the \o% 

 sugar solution sJioiucd no trace of nitrates, diphenylamine entirely 

 failing to call forth the reaction. This experiment suffices to prove 

 that the assimilation of nitrates can take place in the dark, provided 

 there be sufficient sugar present. The quantitative analysis shows 

 the result more clearly. 



(I) Solution containing 0.1% KjHPO^, 0.1% KH^PO^, 0.1% MgSO^, half saturated 

 with CaSO^. 



