6 MASS. EXPERIMENT STATION BULLETIN 379 



workers believe that these elements as components of plant and animal tissue 

 are more efficient than drugs and unquestionably safer to employ. 



The factors that affect synthesis of proteins, fat, carbohydrates, and fiber 

 may play a somewhat similar role in the assimilation and utilization of ash and 

 ash constituents as all groups are more or less interdependent; but the available 

 supply of soil nutrients appears to be more of a limiting factor in ash assimilation 

 than selective absorption. 



Distribution of Ash Constituents 



The soluble ash is a measure of plant assimilation but not of the distribution 

 of its constituents. As previously stated, seasonal and environmental conditions, 

 soil, fertilization, cultural treatment, etc., and the feeding ability of the plant 

 are all factors, but to a considerable extent uncontrollable. The garden fruits 

 exceed the major and minor fruits in ash content, followed by root and leaf and 

 stem vegetables. The remaining groups except some cattle feeds and roughage 

 are low in ash. 



Iron is the most abundant of the trace metals determined and in some instances 

 seems to parallel the soluble ash. The amount increased from fruits and cereals 

 to root vegetables, leaf and stem vegetables, cattle feeds, and roughage. 



Copper is apparently not present to any great extent in most soils or at least 

 is not available, as the amount assimilated by plants varied from 4 to 40 parts 

 per million. 



The amount of manganese in foods exceeds copper. It is of similar distribution 

 but more variable. Two grams of material in many instances will yield only a 

 bare trace of manganic acid. 



A few results on zinc are also reported. These were determined by the 

 original method and may be slightly low in some instances because of incomplete 

 recovery of the zinc from the ash. The amount of zinc in most samples 

 exceeds that of copper and occasionally even that of manganese. The results are 

 inadequate, however, for any generalization. 



The amount of phosphorus in most natural and processed foods is relatively 

 high as compared with the metals so far reported, generally' ranging from 200 to 

 16,000 parts per million, the main portion of which occurs in organic combination 

 with the protein and ether-soluble bodies. The phosphorus content appears to 

 increase from the major fruits to the minor fruits, root vegetables, cereals, rough- 

 age, leaf and stem vegetables, and cattle feeds. 



The analyses show that trace metals are subject to a greater range than the 

 nutrients (proximate analysis). The differences in composition between members 

 of the same group and even between samples of the same variety are so large 

 that a generalization or trend is about all that is permissible. 



