4 POPULAR ILLUSTRATIONS OF 



beard, and at the bottom (e) is the embryo or germ, while (/) 

 represents the flour of the grain, or, as it is called botanically, the 

 albumen of the seed. 



Let us examine the embryo more particularly. As it lies in the 

 seed it can readily be divided into four portions. An upper portion 

 (d), which is the young seed leaf or cotyledon, is single, and there- 

 fore the class of plants to which the wheat belongs is called " mono- 

 cotyledonous." The second portion of the embryo (g) represents 

 the plumule or bud of the plant, while that part marked (i) repre- 

 sents the root or radicle, and the portion between the radicle and 

 plumule marked (K) represents the stem. The embryo is, in fact, to 

 all intents and purposes a young plant, which, like young people, 

 requires a start in life. And this start is given to it by a con- 

 junction of the "circumstances necessary for its existence," which, 

 as before stated, are heat, moisture, and air. 



All the summer the soils of our fields are absorbing heat directly 

 from the sun and stars. Heat is a force and principle in nature 

 which has many most interesting properties, for a description of 

 which I must refer to works on natural philosophy. Water is 

 formed by the chemical union of two gases (hydrogen and oxygen), 

 which are elementary principles in nature, and, like all other 

 chemical compounds, they unite to form water in fixed and definite 

 proportions. By volume this union is as 2 of hydrogen to I of 

 oxygen, the size of an atom of hydrogen being double that of 

 oxygen. By weight the proportions are, hydrogen 1, and oxygen 8 

 the latter atom being eight times heavier than that of the 

 former ; and the combining proportion of water when it unites 

 chemically with other bodies, as it does with sulphuric acid, is 9. 

 Atmospheric air is a mechanical mixture of two gases and a solid 

 body three elementary principles of nature. These are nitrogen 

 (an element which enters largely into the composition of animal 

 structures), oxygen, and carbon. The first two are in the proportion 

 of nitrogen 79 and oxygen 21 parts, less the 1000th part, which is 

 occupied by a union of carbon and oxygen forming carbonic acid a 

 most important part, as we shall see, of the food of plants. 



Let us now proceed to notice what takes place when the seed is 

 brought into contact with heat, moisture, and atmospheric air. 

 First, the embryo plant begins to grow ; the dormant life springs 

 into action ; the bud, enveloped or surrounded by its cotyledon or 

 seed leaf, appears above the ground, while the radicle or root makes 

 a similar movement into the ground below. 



Let us linger a moment and inquire what is meant by " growth." 



The embryo is originally a cell, known as pollen grain, containing 

 molecular matter, that is, matter having the greatest amount of 



