— 2« 



"Sucking" water up a tube is removiug a part of the pressure of the 

 air above the water in the tube. The pressure of the air on the water 

 outside of the tube pushes the water up the tube. 



Enlarging the chest in respiration makes a larger space. The pressure 

 of the outside air crowds in and inflates the lungs to fill that space. 



The toy called a "sucker" — a leather disc with a string in the centre 

 illustrates this further; the pump and the siphon also. 



From pressure of air, we may pass to experiments on bodies floating 

 in the air as balloons — toy balloons, either paper filled with hot air or 

 rubber filled with a gas lighter than air. Next we may take up currents 

 in the air and water. 



It has been seen that heat expands water and air. These are then 

 lighter. The warm water rises in the cold, the warm air in the cooler. 

 We have then the basis for the study of ventilation and winds. 



Flowering Plants. 



The seeds that were planted have now become plants of considerable 

 size and demand further consideration. The following questions may 

 be taken up: What is their food and how do they obtain it? How do 

 they form their seeds? How do they distribute their seeds? Pursuing 

 any of these lines will raise a hundred questions pertaining to the con- 

 trivances by which each kind of plant, through leaf, stem, branch and 

 roots, and the various parts of each, is adapted to its particular kind of 

 life. Studying a?- plant from these points of view will not require 

 learning the names of the parts of the plant except where there is occa- 

 sion to use the name, and also the learning of the technical names of 

 the forms of leaf, stem and root, which are used very rarely except in 

 technical descriptions in Systematic Botany. Although these have in 

 the past formed a prominent part in the conventional courses in Botany, 

 they should have little or no part in Nature Study by children. 



The Plant's Food. 



This consists mainly of (i) carbonic acid, obtained from the air, and 

 (2) water, obtained from the ground, also (3) a small amount of various 

 substances dissolved from the soil by the water. 



To show that plants take up water by means of roots and root-hairs, 

 dig up a plant and carefully wash the dirt from the roots, harming the 

 root and root-hairs as little as possible. Place the root in a bottle or 

 flask, allowing the stem to pass through a cork. The cork is slit and 

 placed around the stem. Through the cork also extends one end of a 

 glass tube bent in such a way as to form a gauge. The tube is filled with 

 water. (This arrangement will be shown in the lecture room.) Very 

 soon the water descends in the tube and continues to do so rapidly, 

 showing that the plant is using up the water. The cork ought to be 

 covered with paraffine so that evaporation from that source can not take 

 place. 



