n, i THE BOTANICAL MAGAZINE. [Vo i. xxi. no. 243. 



net ion of potassium salts, can not be identified with that of 

 calcium salts in counteracting the injurious action of magne- 

 sium salts, although that retarding action of potassium salts can 

 also be observed with phenogams. Young harley plants of 8 cm. 

 hight were carefully deprived of the endosperm in order to 

 exclude the influence of stored up mineral matter, and placed 

 into the following solutions (3 in each flask) : 



I 0.4% Mg(N0 3 ) 2 . 



II 0.4% Mg(N0 3 ) 2 -f0.2% CaS0 4 , 



III 0.4% Mg(NO 3 ) 2 + 0.2% K 2 S0 4 , 



IV 0.4% K 2 S0 4 . 



After 7 days the plants in I were dead, after 15 days two 

 of the plants were dead in III, after 30 days the third was 

 perfectly yellow and 11 days later it died. In IV two of the 

 plants died after 28 days, the last after 36 days, while in II 

 (Ca+Mg) each plant had three green healthy leaves after 8 

 days, while the oldest leaves only had died off. The most 

 remarkable difference was however the growth of the root in 

 this case from 6cm. to 14cm. while in the other three solutions 

 growth had stopped altogether. These plants were still alive 

 five weeks later, the old leaves died, but young one started 

 anew. 



A similar experiment was made with young pea plants. 

 Here only those plants developed branches and reached the 

 flowering stage, which were placed in the solution II. These 

 plants increased in height 20cm., those in III only 6— 8cm., 

 while those in I and IV stopped growth and died gradually. 



When the endosperm of barely shoots is not removed it 

 will take much longer until the toxic effect of magnesium salts 

 causes death. Thus such barley seedings of 6— 8cm. height, placed 

 in 0.20% Mg(N0 3 ) 2 were still alive after 18 days, although the 

 leaves had almost entirely turned yellow. By the simultaneous 

 presence of 0.25% KN0 3 this yellowing had not yet develop- 

 ed so far as in the former case, but it had spread over nearly 

 one half of the leaf area; the former plants died after 31 days, 

 the latter after 40. As to the alleged toxic action of potassium 

 salts may be mentioned that when barley seedlings are deprived 



