208 SEED AND FRUIT DISPERSAL 



seeds. In the ex-albuminous seeds, represented by the bean, 

 pea, peanut and pumpkin, the reserve food all occurs in the 

 cotyledons or seed-leaves. In albuminous seeds represented 

 by coffee, nux vomica, castor oil and flaxseed, the reserve 

 food is stored in the endosperm, a tissue which completely 

 surrounds the embryo. It is the function of the endosperm 

 and cotyledons to provide food for the germinating embryo. 



The reserve material occurring in seeds consists of starch, 

 reserve cellulose, aleurone, fats, oils, alkaloids, glucosides 

 and bitter principles. Sometimes more than one of these 

 substances occur in the same seed. Mustard seed contains 

 aleurone, fixed oil of mustard, which is extracted by pressure, 

 and volatile oil of mustard, which is obtained by maceration 

 and distillation. The bean contains aleurone, oil and starch. 

 Nux vomica contains reserve cellulose, which is changed by 

 ferments to a plant food, and two alkaloids, brucine and 

 strychnine, the latter a well known drug and poison. Linseed 

 contains aleurone and fixed oil; the oil is pressed from the 

 seed and used in the manufacture of paint and the crushed 

 seed-cake with the oil removed is used as a cattle food. 



Embryo, 1 The embryo or immature plant has well defined 

 and differentiated tissues and organs. 



Parts. The typical embryo is differentiated into a bud 

 or plumule which continues the growth of the plant, one or 

 more cotyledons or seed leaves, a hypocotyl or stem below the 

 cotyledons, and a caulicle which develops the primary root. 



The plumule is the highly developed bud with formed 

 leaves which occurs between the cotyledons; frequently the 

 bud between the cotyledons is very small and no leaves are 

 present. The plumule develops the stem and leaves of the 

 seedling. 



The number of cotyledons varies considerably in the seed 

 bearing plants. In the gymnosperms, represented by white 



