POPULAR ILLUSTRATIONS OF 



and emits oxygen ; while the latter emits carbonic acid and absorbs 

 oxygen. They may be diagrammatically represented in the follow- 

 ing figures : 



Proto-phyton (from llgurog, Proto-zoon (from 



first, and 3>urov, a plant). first, and Zuov, an animal). 



These cells are of all shapes, seldom so round as represented in 

 the diagram. They essentially consist of what are termed cell-walls, 

 having one or two layers (a), and of cell contents, which are a fluid 

 represented by the cross-lines ; small particles of matter termed 

 molecules or granules, held in solution by the fluid ; and a nucleus (6), 

 which often contains a still smaller body, termed the nucleolus. Now, 

 these cells exist as separate and distinct beings living, reproducing, 

 and occupying very important positions in the economy of nature. 

 From these cells all living structures, vegetable or animal, are 

 built up. 



It is the Protophyton which will for the present engage our 

 attention ; and I propose to illustrate its development in the vege- 

 table world by describing 



THE NATURAL HISTORY OF A GRAIN OF WHEAT. 



I will commence my history with the grain as it is stored up in 

 the barn of the farmer, or rather just as he is going to plant it in 

 the autumn. If the seed is examined, a small whitish spot will be 

 noticed on the lower part of the back. This is the germ of the 

 future plant, which if placed under certain circumstances will have 

 its dormant life called into action, and will begin to grow. 



Now in the very threshold of our inquiry we see a most beautiful 

 provision, and are met with a very perplexing question What is 

 life ? This question has puzzled wiser heads than my own. It 

 cannot, in fact, be answered. And why ? Simply because the mind 

 of man is finite, and life is one of the attributes of Infinity. We 

 have nothing with which we can compare it, and therefore as man's 

 reason essentially depends upon the power of comparison, we cannot 

 nor ever will solve the difficulty. 



There has been a tendency in the discussions of recent days to 

 identify the vital with the physical forces of attraction, as evinced in 



