the large end with the exposed membrane is beneath the water. After several hours, observe the tube on top of the egg to see whether the water has forced its way into the egg and increased its volume so that part of its contents are forced up into the tube. If no tube is at hand, see whether the contents are forced through the hole which has been made in the small end of the egg. Explain how the law of osmosis is verified by your result. If the eggshell contained only the membrane, would water rise into it? If there were no water in the bottle, would the egg-white pass down into the bottle? =42.= _The region of most rapid growth._ The pupil should make marks with waterproof ink (as Higgins’ ink or indelible marking ink) on any soft growing roots. Place seeds of bean, radish, or cabbage between layers of blotting paper or thick cloth. Keep them damp and warm. When stem and root have grown an inch and a half long each, with waterproof ink mark spaces exactly one quarter inch apart (Figs. 48, 49). Keep the plantlets moist for a day or two, and it will be found that on the stem some or all of the marks are more than one quarter inch apart; on the root the marks have not separated. The root has grown beyond the last mark. NOTE TO TEACHER.--The microscopic structure of the root can be determined only by the use of the compound microscope; but a good general conception of the structure may be had by a careful attention to the text and pictures and to explanations by the teacher, if such microscopes are not to be had. See note at close of Chapter X. CHAPTER IX THE STEM--KINDS AND FORMS; PRUNING =The Stem System.=--The stem of a plant is the part that _bears the buds_, _leaves_, _flowers_, _and fruits_. Its office is _to hold these parts up to the light and air_; and through its tissues the various food-materials and the life-giving fluids _are distributed to the growing and working parts_. The entire mass or fabric of stems of any plant is called its =stem system=. It comprises the trunk, branches, and twigs, but not the stalks of leaves and flowers that die and fall away. The stem system may be herbaceous or woody, annual, biennial, or perennial; and it may assume many sizes and shapes. =Stems are of Many Forms.=--The general way in which a plant grows is called its =habit=. The habit is the _appearance or general form_. Its habit may be open or loose, dense, straight, crooked, compact, straggling, climbing, erect, weak, strong, and the like. The roots and leaves are _the important functional or working parts_; the stem merely connects them, and its form is exceedingly variable.