38 GROWTH OF THE PLANT 



25 to 17 per cent, organic acids, particularly amino-acids, 

 organic bases, and mineral salts of potassium, magnesium, 

 calcium, and iron. 



34. Seeds.— In providing for a continuation of itself the 

 following year the plant has several ways of storing up 

 food to be used before new roots and leaves can provide 

 bodily substance for the new plant. Sooner or later crop 

 plants bear seeds which contain carbohydrates, oils, and 

 proteins, all in the most concentrated and dehydrated 

 form. Carbohydrates occur in the form of starch (Fig. 6, 

 c and d); and proteins occur in the granular or crystalline 

 form usually called aleurone grains (Fig. 6, b). The oils 

 are packed away as minute drops (Fig. 6,/). There is 

 little water present in the seed (Sections 2 and 98), and but 

 little space is occupied by the food materials. During the 

 formation of seeds most of the plant activities are devoted 

 to the solution and transportation of material from the 

 leaves and stems, where it has been temporarily lodged, 

 to the seeds, where it is changed to the insoluble form and 

 packed away. Dextrose is dehydrated and made into 

 starch, or reduced and made into oils; in some cases largely 

 starch, as in cereals, in others largely oils, as in cottonseed. 

 Peptones and albumoses are dehydrated and made into 

 proteins. 



35. Roots, Bulbs, and Tubers. — Some plants do not bear 

 seeds the first year, but go into a resting stage for a time and 

 the following year produce seed. These are the so-called 

 biennials. To get a start the second year they must have a 

 store of material from which to build new plant substance 

 before roots and leaves can do their work. Consequently 

 they form enlarged fleshy roots, like the beet; underground 

 stems or tubers, like the potato; or enlarged stalks called 

 bulbs, like the onion. In these storage organs the car- 

 bohydrates, oils, and proteins are not usually packed away 

 in a dry, concentrated form. In the beet carbohydrates 

 take the form of sucrose; in the onion, of dextrose, but in 

 the potato, of starch. Oils and proteins are not present to 

 any extent. If the latter are present, however, they occur 

 not as aleurone grains, but in a more hydrolyzed form, even 



