How a Tree Lives 69 



head and becomes flabby and withers. In a twig the 

 walls are stiffened so that they stand firm however little 

 water there is. 



PRACTICAL WORK. 



Place a young shoot and a twig in a glass without water. You 

 will want them in question 5. 



1. Test the solubility in water of washing soda, borax, nitre, etc. 

 Proceed as follows : look closely at the substance and crush it up in 

 the mortar with the pestle. Pour it into the beaker, and fill the 

 latter about three-quarters full of hot distilled water. Place it on 

 the wire gauze and let it boil for some minutes, stirring occasionally. 

 Fold the filter paper in half and then again in half, and fit it into 

 the funnel and moisten it. Fasten the funnel into the stand. Place 

 the porcelain dish under it. Stir up the water in the beaker and 

 pour it into the funnel. When it has all filtered into the dish, place 

 the dish on the sand bath and let the water gradually boil away. 

 While waiting for this you can go on with the next question. When 

 the dish is dry examine it to see if the water has left anything 

 behind. If so find out if it is the same as what you had at the 

 beginning. According to whether there is left much, little, very little, 

 or none of it write soluble, slightly soluble, very slightly soluble or 

 insoluble next to the name of the substance on the paper. (Fig. 36.) 



It is sometimes quicker to take just a few drops of the filtered 

 liquid in a watch-glass and put the watch-glass either on a radiator 

 or over the steam escaping from a flask of boiling water. The less 

 water there is to evaporate the sooner you will find the answer and 

 be able to go on to the next question. 



2. Try the same test with garden soil, leaf mould, sand, peat, 

 clay ; also with the substances used as fertilizers, crushed bones, 

 kainite, mineral superphosphate, lime, sulphate of potash and 

 magnesia ; also with any chemicals employed in the botanical labora- 

 tory for water culture solutions such as potassium nitrate, calcium 

 phosphate, magnesium sulphate. 



3. Prepare a series of salt solutions of various strengths. First 

 a solution containing 32 grms. per litre. This will taste about 

 as strong as sea water. Take 500 c.c. of it and dilute with 500 c.c. 



