i8 THE BOOK OF NATURE STUDY 



is wet through, the soil underneath remains dry. If the tips 

 of the lateral roots did not reach the circumference, only soaking 

 rains would be of any value to the tree. Teachers living in the 

 country might encourage their pupils to observe the root-systems 

 of trees as far as possible. They might notice, for instance, 

 the exposed roots of the beech, supporting itself one hardly 

 knows how on the deep banks of a country lane. Or the Scotch 

 Fir (Finns sylvestris) may be examined. This tree lives on dry, 

 sandy soil, and is not usually easily uprooted, for the main root 

 is deep and gives off widespreading lateral roots. When one of 

 these trees is found uprooted, it will probably be seen that it 

 has been growing in shallow soil, and has therefore only been 

 able to form a short main root. Sometimes two trees, the one 

 having a deep-rooted, the other a shallow-rooted, system, are 

 found growing together. The oak and the beech are examples 

 of this. The former strikes its roots into the soil sometimes to 

 a depth of 5 feet, leaving plenty of room for the shallower system 

 of the beech, and at the same time profiting by its association 

 with the beech, whose leaves furnish it with humus. 



CONDITIONS OF GERMINATION. So far, the first stages of 

 germination have been considered, namely 



(a) The protrusion and growth of the radicle. 



(6) The emergence of the cotyledons above the soil in many 

 seeds. 



Before going on to describe the development of the shoot 

 from the plumule, it will be as well to consider more exactly 

 the conditions necessary for germination, and, in fact, for the 

 life of the plant. And here the teacher should proceed by means 

 of experiments, in order to develop the reasoning power. The 

 experiment should be as simple as possible, should be suggested 

 by the student, and should be carried out with as simple apparatus 

 as possible. In some laboratories unnecessarily expensive appar- 

 atus is sometimes provided. This is a disadvantage, for the 

 simpler the experiment, the more likely is a student to repeat 

 it at home. 



To proceed from the known to the unknown is a very 

 sound principle. It will be natural, therefore, to inquire whether 



