LIVING CONDITIONS; THE SEED 65 



dener or farmer places his seeds in the ground, and they sprout. 

 Should we conclude that the soil somehow causes the seeds to 

 begin their active growth after their long rest? The soil is 

 a mixture of many kinds of stuff, some of which may have 

 something to do with the sprouting. But others of them may 

 have nothing at all to do with it. To find out just what it is 

 that causes the sprouting we must consider the effect of each 

 of the various factors of the seed's surroundings by itself. 



54. The environment. Now, in what ways do the conditions 

 surrounding a seed in the ground differ from the conditions in 

 a box or a jar? There may be a difference as to temperature, 

 or as to the air, or as to the amount of water, or as to the light, 

 or as to some of the chemical substances present in the soil. 

 Experiments have been made with every one of these factors. 

 We can also answer this question in part from our experience. 



Most of us know that seeds kept in jars will not sprout, 

 whether they are kept in the dark or exposed to light. Putting 

 seeds in the ground brings about their germination not on 

 account of darkness but on account of some other factor. We 

 also know that seeds kept in a warm place and seeds kept in a 

 cool place will both fail to sprout so long as they remain in our 

 jars or boxes. The soil may be cooler than our storeroom, or 

 it may be warmer ; but it is not this that makes them sprout in 

 the ground. Perhaps the soil keeps some of the air away from 

 the seed ; but keeping air out of the jar will not make the seeds 

 sprout. So it cannot be the absence of air by itself, or the 

 presence of air by itself, that causes the seeds in the ground 

 to germinate. 



In regard to the chemical substances in the soil, our usual 

 experience tells us nothing at all. Are there certain substances 

 that cause the sprouting? We might find out by trying some 

 of them. The chemist can tell us what there is in the soil, and 

 he can also prepare the different kinds of stuff in a pure condi- 

 tion; but if we place the seeds in boxes containing the various 

 ingredients of the soil, such as sand, clay, and various salts, we 

 shall find that not one of the seeds sprouts. This suggests that 



