118 THE FUNCTIONS OF 



cultures were supplied with a complete culture solution which 

 included 0-25 p. p.m. of boron as boric acid. From the beginning 

 of the third week, two series of cultures receiving no calcium and 

 four supplied with a nutrient solution containing 170 p. p.m. of 

 calcium, received different amounts of boron. These treatments 

 were continued for 10 days, at the end of which time the dry 

 weights of the shoots, the total calcium and boron content and 

 the contents of soluble calcium and soluble boron of the shoots 

 were determined. The various treatments and the results obtained 

 from them are indicated in Table XV. 



Table XV. Calcium and boron content of maize supplied with 

 different amounts of boron. (Data from Marsh and Shive) 



Concen- 

 tration Dry weight Total Ca Soluble Ca Total B Soluble B 

 of boron of shoot per g. of per g. of per g. of per g. of 

 supplied per plant dry matter dry matter dry matter dry matter 

 p.p.m. g. mg. mg. mg. mg. 



No calcium supplied in nutrient solution 

 0-0 1-50 30 0-3 0-001 00005 



0-25 2-60 30 1-0 0-008 00069 



170 p.p.m. calcium supplied in nutrient solution 



00 2-85 7-6 2-1 0-002 00015 



0-1 5-40 7-7 2-4 0-005 0-0042 



0-25 5-30 80 2-8 0-008 0-0070 



50 4-37 7-7 4-2 0-025 00232 



Inspection of these results shows that the total calcium content 

 of the shoots is independent of the amount of boron supplied ; 

 on the other hand, the soluble calcium content runs parallel 

 with both the soluble boron content and the total boron content 

 of the plant and also with the boron content of the medium. It 

 is therefore concluded that the soluble calcium content is deter- 

 mined by the boron content, a large proportion of which is in 

 a soluble form, and which is itself determined by the boron 

 content of the medium. 



There is thus, according to Shive (1941), a difference between 

 dicotyledons as exemplified by Vicia Faba (and presumably 

 Glycine hispid a) and monocotyledons as exemplified by Zea mais, 

 in that in the former the calcium and boron contents are gener- 

 ally much higher than in the latter, but in the dicotyledons 

 studied only a small fraction of the boron is soluble, whereas in 



