10 Elementary Principles of Agriculture 



15a. Have the pupils make a list of all the common plants 

 with which they are familiar that are started from seeds; also, those 

 that are started from bulbs, roots, and cuttings. 



16. Structure of Seeds. When we look at a bean, we 

 see it is covered with a thin skin, or "seed-coat," which 

 is quite smooth except at the edge where it was attached 

 to the bean pod. Now, if we remove this coat from a 



seed (using one that has been 

 soaked in water over-night), two 

 large, thick " seed leaves," or 

 cotyledons (cot-y-le-dons) , joined 

 to a minute stem, may be seen. 

 (Fig. 8.) One end of the stem is 

 round and plump, while the other 

 bears two tiny leaves. The latter 

 Fig. s. Bean seed split open i s the stem end, and bears the 

 young bud. The root grows from 



the other end. Thus we see that the bean has all the 

 parts of a plant, but a very small or embryo plant. 



17. Stored-up Food in Seeds. Plants need food to 

 build up their bodies and provide energy, just as animals 

 do. The cotyledons do not look like ordinary leaves, 

 because they are filled with much starch and other 

 substances, to nourish the plantlet when it begins to 

 grow. Substances stored up in seeds like this are called 

 " reserve foods." The reserve food in the case of the 

 bean is largely starch. In some plants it is largely oil, 

 as in cotton seed, sunflower, pecan, flax, etc. Besides 

 starch and oils, another class of substances is present 

 as a reserve food of all kinds of seeds, called pro- 

 teids. Proteids from animal bodies are familiar, as the 

 whites and yolks of eggs, clabber of milk, clot of 

 blood, etc. (See Appendix C.) 



