58 SEEDS AND FRUITS 



forming only a thin covering, which is usually tightly pressed 

 against the inner side of the ovary wall. 



In general structure seeds are similar, all having an embryo, 

 stored food, and seed coat, but in size, shape, and in features 

 which pertain to the structure of the embryo, composition of the 

 stored food, and character of the seed coat, seeds vary widely 

 and can be used in many ways by man. The number of coty- 

 ledons developed by the embryo is used as a basis upon which to 

 classify the Flowering Plants into two classes, Monocotyledons 

 and Dicotyledons. From the stored food, whether stored as 

 endosperm or in the embryo, various valuable products, such as 

 starch, protein, fats and oils, are obtained; and from the hair- 

 like outgrowth of the seed coat, as in case of Cotton, various fiber 

 products are made. Although seeds may be divided into many 

 types on the basis of their structure and external features, only 

 those types which include the most common seeds will be studied 

 in this presentation. 



Bean Type of Seeds. Of this type of seeds, those of the 

 Bean, Pea, Peanut, Clover, Vetch, Alfalfa, Cotton, Pumpkin, 

 Squash, Melon, Apple, Peach, Oak, Hickory, and Walnut are ex- 

 amples. The type is so named because it is characteristic of the 

 Bean family (Leguminosae) , a family notable for its many valu- 

 able cultivated forms among which are Clover, Alfalfa, Beans, 

 Peas, Vetch, and Peanuts. The type is also characteristic of the 

 Rose family (Rosaceae), the family to which most fruits, such as 

 the Apple, Peach, Pear, Cherry, etc. belong. In this family, 

 however, it is the fruit (rarely the seed) that is important. 

 The seeds of the Bean type are common to a number of 

 plant families and to species and varieties of plants so numer- 

 ous that a list naming them all would require a page or more. 

 Although many are valuable commercial seeds, some are borne 

 by weeds and hence of interest because of their undesirable 

 features. 



These seeds differ from other types in having little or no endo- 

 sperm. As the seed develops, all or almost all of the food tis- 

 sue formed by the endosperm nucleus and adjacent cytoplasm 

 is absorbed by the embryo where it is stored in the cotyledons, 

 which, consequently, are so much enlarged that they are much 

 the largest part of the embryo. (Fig. 63.) For this reason 

 these seeds are called exalbuminous seeds, that is, seeds without 



