Structure of Seeds 



11 



18. Corn. The corn " grain " is covered with a clear 

 skin, or seed-coat.* If we cut through a corn grain, as 

 shown in Fig. 9, we see a yellowish oily 



germ, or embryo, on one side, and a large 

 starchy mass of additional reserve food 

 stored back of the germ. When the re- 

 serve food is stored outside of the germ, 

 it is called endosperm. The endosperm in 

 the corn grain exists in two layers, one 

 of which is starchy and loose, and the 

 other clear and hard. 



19. Cotton. In cotton, the seed-coat 

 is covered with a layer of fibers, or lint. 

 The hard brownish coat encloses an em- 

 bryo cotton plant, with leaves closely 

 rolled around the stem. The parts are 

 best made out in seeds that have just 

 germinated. Cotton seeds are very rich 

 in oils and proteids. 



QUESTIONS 



Fig. 9. Section of 

 a grain of corn 

 showing the 

 parts of the germ 

 or embryo corn 

 plant (A, B and 

 E), and position 

 of reserve food. 

 A, root end and 

 B shoot end of 

 embryo; E, the 

 part of the em- 

 bryo that ab- 

 sorbs the reserve 

 food during ger- 

 mination; C, soft 

 starch; D, horny 

 part of reserve 

 Food. 



1. In what other ways than by seeds may plants 

 Start new individuals? 2. Name the parts of a plant 

 that are enclosed in a bean seed. Describe them as 

 they are in the seed. 3. Of what use are the cotyledons? 4. What 

 is meant by reserve food? 5. What substances may be present in 

 reserve foods? 6. Describe the corn seed. 7. What is the essential 

 difference between the bean seed and the corn seed? 8. Describe 

 the cotton seed. 9. Is it most like the corn seed, or the bean seed? 

 that is, in what part of the seed is the reserve food stored? 



*In reality, the covering of a grain of corn is double, but the two coats are 

 so closely united that it is difficult to distinguish them without special prepa- 

 ration. The outer coat corresponds to the pod, or seed-case, as in beans. 



