10 MASS. EXPERIMENT STATION BULLETIN 374 



minor constituent except in nuts. Fiber was present in nearly all products, 

 and it may be noted that fiber tends to increase in most products, except 

 fruits, with maturity and overripeness. 



The soluble ash of natural food products varied with environmental 

 conditions and the feeding capacity of plants. Insoluble ash, largely 

 silica, was frequently traceable to the retention of soil particles in the 

 interstices of leaves and stems. When the retained soil exceeds 0.50 per- 

 cent of the ash, the determination of minerals may be vitiated. 



The data given in the table seem to warrant the following deductions: 

 The major fruits are noted for their high carbohydrate content; minor 

 fruits have less carbohydrate and more protein, fat (wax), and fiber; rasp- 

 berries and blackberries are relatively high in crude fiber. Beans and 

 peas, in common with most leguminous crops, contain considerable pro- 

 tein, and some varieties, especially soybeans, have a high fat content. 



The leaf and stem vegetables constitute a diversified group. Wide 

 variations are found in the same variety of plant grown under different 

 environmental conditions. Onions, cabbage, cauliflower, celery, and let- 

 tuce frequently varj^ 50 percent in their nitrogen-free extract, and the 

 quality seems to improve with increase of the extract. Onions are low 

 in protein, and asparagus is high. Leaf greens, celery, and lettuce are 

 fairly high in protein and ash. Most root vegetables are high in carbo- 

 hydrates, and mangels and radishes contain more than average amounts 

 of protein and ash. Low-fiber cereals are similar to root vegetables in 

 total extract, but they contain more starch. High-fiber cereals contain 

 about the same amount of crude protein as the low-fiber cereals, and 

 slightly less total extract. 



Processed human foods resemble the cereals from which they are de- 

 rived. Cattle feeds are industrial by-products and vary in accordance 

 with their sources and treatment. Forage plants, fed green or dried to 

 farm animals, are naturally high in fiber and ash; and when they are 

 freshly cut, they contain considerable protein. This is especially true of 

 leguminous forage. 



Environmental factors that aflfect the synthesis by plants of the nutrient 

 materials may have a similar eflfect on the plants' assimilation and uti- 

 lization of ash constituents. The available supply of minerals in the soil 

 seems to be a more limiting factor than selective absorption in the min- 

 eral intake by plants. The following deductions are presented from the 

 results of the analyses: 



Garden fruits exceed major and minor fruits in ash content; root, leaf, 

 and stem vegetables are similar to the garden fruits; and cereals, processed 

 human foods, nuts, and cattle feeds are relatively low in ash. 



The minerals are subject to greater variations than nutrients by prox- 

 imate analysis. The difTerences in mineral content among members of 

 the same plant group, and even among samples of the same variety, were 

 so large that a generalization is all that is justified. 



Iron is more abundant than copper or manganese and seems to parallel 

 the soluble ash in some instances. The percentage is increased from 

 fruits and cereals through root vegetables, leaf and stem vegetables, cattle 

 feeds, and roughage. Copper is either not present or not available in 

 most soils, as the amount found in most plants ranged from only 4 to 40 

 parts per million. The amount of manganese in the foods exceeds copper; 



