54 Report of the Acting Director and Chemist of the 



Chlorine. — The fimclion of chlorine in connection with the 

 development of plants is not satisfactorily settled. There are some 

 reasons for believing that some of the compounds of chlorine, 

 especially the potassium chloride (muriate of potash), are instru- 

 mental in transferring starch from the leaves, where it is formed, to 

 tlie flower and fruit. 



Silicon. — It is an unsettled question as to what silicon does in 

 plant growth. Some have thought that its functions might be to 

 give stiifness to slender stems in the case of such plants as grasses, 

 sedges, etc., but there are some serious objections which interfere 

 with the complete acceptance of such a proposition. 



Calcium forms a part of several compounds found in plants. Its 

 chief function appears to be that of strengthening cell-walls. It is 

 often found united with different acids forming cal-cium (or lime) 

 salts. Thus, in beet leaves, we find the salt calcium oxalate. In 

 what specific way it otherwise aft'ects the growth of plants, we do 

 not yet know definitely. 



Potassium compounds are essential to the formation and trans- 

 ference of starch in plants. Starch is known to be first formed in 

 the leaves of plants, after which in some way it becomes soluble 

 enough within the plant-cells to enable it to pass through the cell- 

 walls gradually and later to be carried into the fruit.^where it 

 accumulates and changes back to its insoluble form. It is well 

 established that potassium compounds are intimately connected with 

 the formation of starch in the leaves and with its transference to the 

 fruit. 1^0 otiier element can take the place of potassium in per- 

 forming this work. For the carrying of starch a minute amount 

 of calcium (lime) and chlorine appears to be needed in addition to 

 the potassium. Potassium compounds are important on account of 

 their influence upon the development of the woody parts of stems 

 and the fleshy portions of fruit. Again, potassium compounds are 

 present in those plant juices, which are rather sour; in these 

 cases, the potassium is combined as an acid salt with such acids as 

 citric, malic, tartaric, oxalic and other acids. 



Iron is essential to the formation of the green-coloring-matter of 

 plants called chlorophyl. In the absence of iron, leaves lose their 

 green color and become pale or v/hite and no starch is formed. 



Magnesium closely resembles calcium in many ways, but can not 

 replace it in plants. Magnesium appears to be associated with nitro- 

 gen in the formation of protoplasm ; it also appears to have some 



