4 6 



PLANT BIOLOGY 



SUOGESTIONS (Chaps. VII and VI II). 25. Tests for food. Ex- 

 amine a number of roots, including several fleshy roots, for the 

 presence of food material, making the tests used on seeds. 26. 

 Study of root-hairs. Carefully germinate radish, turnip, cabbage, 

 or other seed, so that no delicate parts of the root will be injured. 

 For this purpose, place a few seeds in packing-moss or in the folds 

 of thick cloth or of blotting paper, being careful to keep them moist 

 and warm. In a few days the seed has germinated, and the root 

 has grown an inch or two long. Notice that, except at a dis- 

 tance of about a quarter of an inch behind the tip, the root is 

 covered with minute hairs (Fig. 44). They are actually hairs ; 

 that is, root- hairs. Touch them and they collapse, they are so 

 delicate. Dip one of the plants in water, and when removed the 

 hairs are not to be seen. The water mats them together along 

 the root and they are no longer evident. Root-hairs are usually 

 destroyed when a plant is pulled out of the soil, be it done 

 ever so carefully. They cling to the minute particles of soil 

 (Fig. 46). The hairs show best against a dark background. 

 27. On some of the blotting papers, sprinkle sand ; observe how 

 the root-hairs cling to the grains. Observe how they are flat- 

 tened when they come in contact with grains of sand. 28. Root 



hold of plant. The 

 pupil should also 

 study the root hold. 

 Let him carefully pull 

 up a plant. If a plant 

 grow alongside a 

 fence or other rigid 

 object, he may test 

 the root hold by se- 

 curing a string to 

 the plant, letting the 

 string hang over the 

 fence, and then add- 

 ing weights to the 

 string. Will a stake 

 of similar size to the 

 plant and extending 

 no deeper in the 

 ground have such 

 firm hold on the soil ? 

 What holds the ball 

 of earth in Fig. 50? 



FIG. 50. THE GRASP OF A PLANT ON THE PARTI- 

 CLES OF EARTH. A grass plant pulled in a garden. 



29. Roots exert pressure. Place a strong bulb of hyacinth" or 

 daffodil on firm-packed earth in a pot j cover the bulb nearly to 

 the top with loose earth ; place in a cool cellar ; after some days 



