HISTORICAL INTRODUCTION 3 



mental work and many field observations have gone to confirm 

 Bertrand's view. 



In 1914, by the use of water-culture experiments with care- 

 fully prepared culture vessels and nutrient salts, Maze showed 

 that not only manganese but zinc also was necessary for the 

 growth of maize. As a result of later work on similar lines he 

 claimed that aluminium, boron, chlorine and silicon were all 

 essential in small amounts for the healthy growth of plants. Of 

 these various elements, boron had already been found by 

 Agulhon (1910) to induce an increased production of dry matter 

 in wheat, oats and radish grown in sand cultures and in maize, 

 colza and turnip grown in field-plot experiments. It is, however, 

 scarcely correct, as has sometimes been done, to quote Agulhon 

 as the first worker to point out the essential nature of boron for 

 higher plants. As Dennis and O'Brien (1937) have pointed out, 

 Agulhon provided no proof that normal growth was not possible 

 without boron, and the credit for first calling attention to the 

 necessity of this element for any plant is due to Maze. The 

 importance of boron as an essential plant nutrient was brought 

 into prominence in 1923 by Miss Warington, who showed by 

 means of water cultures that while a concentration of boric acid 

 as low as 1 in 12-5 xlO 6 was sufficient to allow the normal 

 growth of the broad bean (Vicia faba), in complete absence of 

 boron death of the plant supervened after the development of 

 quite characteristic pathological symptoms. A few years later 

 Sommer and Lipman (1926) added cotton, castor oil, buckwheat, 

 flax, mustard and barley to the list of plants for the growth of 

 which a supply of boron is essential. Since then the list of such 

 species has been further extended. 



Confirmation of Maze's finding that zinc is necessary for the 

 healthy development of maize has been provided by more 

 recent observations of Barnette and Warner (1935), Mowry and 

 Camp (1934) and others, who have shown that the curious 

 chlorotic condition of this plant known as ' white-bud ' can be 

 cured by application of zinc sulphate. Sommer and Lipman 

 (1926) also found zinc essential for the growth of sunflower and 

 barley, and later Sommer (1928) reported that buckwheat and 

 beans could only undergo normal development in presence of 

 zinc. In beans, for example, abscission of leaves and flower buds 



