DAIRY AND SEED IMPROVEMENT MEETINXS. 383 



must not be inferred that other causes will not also delay the 

 maturity of the onion, for this will happen if there is a serious 

 lack of any one of the essential elements, although a lack of 

 lime and failure to use a fertilizer with a high percentage of 

 soluble and available phosphoric acid are usually the chief causes 

 of thick necks, and of this delay in ripening. 



CONCERNING MAGNESIAN LIMESTONE. 



It is universally recognized that magnesia is essential to plant 

 growth and that no other substance can wholly take its place. 

 According to Hilgard and Loew, magnesia acts as a carrier of 

 phosphoric acid in the plant, a fact supported by its abundant 

 presence in oily and starchy seeds. It has also been shown by 

 Reed that a rather definite relation seems to exist between mag- 

 nesia and the formation of vegetable oils. 



There can be no escape from the conclusion that magnesia is 

 concerned in the most important synthetic or "building up" pro- 

 cesses of the plant. It seems to be true that occasional soils 

 are so lacking in magnesia that its application is helpful by virtue 

 of the direct plant food functions which it is able to perform. 

 In the course of my experiments with it in Rhode Island it was 

 occasionally noticeably helpful even when ample lime was used. 



A few years ago, Loew called attention to the fact that some 

 soils contain already relatively high percentages of magnesia, 

 and that in such cases if lime is deficient, the magnesia may have 

 a poisonous action. Unfortunately, he and some of his pupils 

 and assistants appear to have made altogether too much of this 

 point, as has been recently shown in Germany, by Gile in Porto 

 Rico, and still earlier by Wheeler and Hartwell in Rhode Island. 



It must be remembered that all magnesian limestones carry 

 lime as well as magnesia, and hence there need be no fear of 

 immediate ill effects from magnesia, even when ground mag- 

 nesian limestone is employed. It may, nevertheless, be a wise 

 precaution on soils already containing an excess of magesia, 

 either to use a limestone carrying only a small percentage of 

 magnesia or else to alternate by applying a pure limestone 

 between every one or two applications of the magnesian lime- 

 stone. Probably a very low percentage of magnesia in the lime- 

 stone will meet any possible need of magnesia which may exist 

 in any of our soils. 



