42 SEEDS AND SEEDLINGS. 



Bean and Pea seedlings exposed to light, with their roots 

 in distilled water, grow for several months and may even pro- 

 duce flowers, though they are small and weakly as compared 

 with seedlings grown in soil or in a culture solution. Small 

 seedlings, with scanty food-stores e.g. Mustard live only a 

 few weeks when exposed to light and supplied with distilled 

 water, and for a shorter time when kept in darkness. 



* (a) Deprive Beans and Peas of one or both cotyledons, and observe 

 the result. Remove the cotyledons, in different cases, (1) just after 

 the seed has been soaked, (2) after the root has grown 2 ins. long, 

 (3) after the plumule has grown 2 ins. long. 



* (6) Grow various seeds in jars containing distilled water, fixing them 

 either into holes in muslin or flannel, or into split or bored corks ; fill 

 up the water as required, but always use distilled water. Keep some 

 of them in darkness, expose others to the light, and compare their 

 growth and their increase or decrease in dry weight. Another method 

 is to let the roots grow into sand that has been washed thoroughly with 

 tap-water and then with distilled water, using the latter for watering. 



72. How is Food transported? The foods produced by 

 the action of ferments are soluble, and therefore able to travel 

 to the places where they are needed, to supply material and 

 energy for the growth of the young root and shoot. It is 

 easy to trace the passage of the digested foods, especially in 

 the case of sugar, because whenever the sugar accumulates 

 some of it is usually changed back temporarily to starch. 



* In seedlings of Bean, Pea, and other plants you are growing, note 

 that the root and shoot of the ungerminated seed as a rule contain no 

 starch, but that after germination has begun starch appears in the 

 young root and shoot ; cut these parts longitudinally, and apply iodine 

 solution to the cut surfaces. 



73. Energy furnished by Foods. The amount of energy 

 supplied by a food may be found by measuring the heat pro- 

 duced by burning it, and it is therefore called the fuel value. 

 The fuel value of carbohydrates and proteids is about the 

 same, that of fats is more than twice as great. In plants, 

 as in animals, the energy is obtained from the food by 

 oxidation (= burning), and carbon is the principal substance 

 burned, setting free carbon dioxide. Burning 1 gramme 

 of carbon sets free enough energy to raise 8 kilograms 

 (=r about 2 gallons) of water from to 1C., and about 



