12 POPULAR ILLUSTRATIONS OF 



unchangeable. But man builds a very different house when civilised 

 to that which he raises in his primeval forest. 



Now just as instinct differs from reason, so does physical differ 

 from vital force. The crystal attracts its elements from their 

 solution in water, and takes upon itself its destined form now as it 

 ever did in obedience to natural law, which is purely physical. But 

 the cell of the wheat-plant selects the flint to strengthen the sides 

 of the hollow cylinder of straw with reference to the existence of a 

 world. If that power of selection did not exist in the cells of the 

 wheat-plant and other grasses, all our cattle, and every human 

 being on the face of the earth, would perish. The law of attraction 

 fails to explain the act upon which such a vast issue depends. The 

 unconscious plant-cell must be a passive agent. It yet performs an 

 act far higher than anything human reason can effect. 



Again, how irresistibly, and yet how unconsciously, are we led 

 step by step from the physical to the vital from instinct to reason, 

 and from reason to the Infinite ! 



CHAPTER IH. 

 THE NATURAL HISTORY OF A GRAIN OF WHEAT 



(continued}. 



THE next stage we note in the history of our young plant is, that 

 the stem forms leaves. Bearing in mind the modes in which cells 

 multiply so as to constitute growth, we can understand how the leaf 

 buds out of the node, and gradually grows to the length and shape 

 so well known in the wheat-plant. 



This leaf is oblong and lancet-shaped. It is covered at its basal 

 attachment to the stem by a split sheath, and, if minutely examined, 

 will be found to possess a short stalk or petiole ; and at the 

 point of junction of the petiole and blade, there is a membranous 

 expansion, called a ligule. I need not illustrate all this, as plants 

 for examination are always accessible even in winter. 



Then, observe the leaf has two surfaces of different colours, one 

 looking upwards, of a dark green, owing to the presence in its 

 surface cells of an excess of a fluid containing a pigment known as 

 "chlorophylle," which is the universal cause of the green colour of 

 vegetable life. The other surface, looking downwards, is of a paler 

 colour, owing to the fact that many of the cells contain air instead of 

 " chlorophylle." 



Now these air chambers have a certain analogy to the air cells of 

 our own lung, for with the openings by which they communicate 



