I. You will observe by the cuts in this exe that plants have various kinds of roots. Study t forms carefully and see if you can think of any vantages in each particular kind.

2. Make a list of plants and group them in the lowing table, according to their form of root syst

Air Roots Fleshy

1. Do air roots take in plant food?

2. What difference do you notice in the app ance of the roots of trees which have long been posed to the air by the soil having been was away?

3. Why do some plants send their roots deep i the soil while others keep them near the surface 4. Does the amount of plant food or moisture fect the depth to which plants send their roots in soil?

DIRECTION OF GROWTH OF ROOTS

TIME: WHEN WEATHER IS WARM

Object: To learn the direction of root growth and the things which influence this direction.

Material needed: Peas, soil, tumbler, small dish, three clothes-pins, mercury, wooden box (12 x 10 x 3 inches), wire netting, sawdust, blotting paper.

DIRECTIONS

1. Place some peas which have germinated upon moist soil with the radicles (roots) pointing in different directions. Cover with a glass to prevent evap

FIG. 12-SPROUTING BEANS

oration and watch closely. Do the root-tips point downward? Do you think the tips of the roots drop downward by their own weight?

2. Fasten three clothes-pins to the side of a small dish, and pour into it some mercury. To each of the clothes-pins pin germinating peas and allow the tips of the roots to rest on the surface of the mercury. Pour on enough water partly to submerge the seeds. What direction do the tips of the roots take? Do they bend by their own weight?

3. Does light, moisture, air, warmth, or food influence the direction of growth? Let us carry the experiment further. In a small box, not over 3 inches deep, having a bottom of wire netting and filled with damp sawdust to one half its depth, place some seeds which have just started to germinate and fill the box with sawdust of equal moisture with that in the bottom of the box. Now cover with blotting paper or cloth and keep moist. Hang up the box so the bottom can be observed.

You will observe: (1) that air, light, and warmth, come mostly from below; (2) moisture is about equally abundant above and below; (3) and the same amount of sawdust is above and under the seed.

Now, why does the root grow downward?

ARTIFICIAL ROOT-HAIR

TIME: FALL OR SPRING TERM

Object: To represent by artificial means the manner in which root-hairs take in plant food.

Material needed: Egg, vinegar, glass tube, sugar, tumbler, thread.

DIRECTIONS

1. Break a small hole in one end of an egg and pour out the contents; soak the shell in weak acid or vinegar until the shell is dissolved. Insert a small glass tube into the membrane and tie firmly.

2. Now pour into the tube a thick sirup, made of sugar and water, until it rises a short distance above the membrane. Mark the height to which the sirup stands and submerge the membrane in a tumbler of water. What happens to the liquid in the tube?

3. Make a stronger sirup and submerge the membrane in it and note what happens to the fluid in the tube.

Facts.-Root-hairs act in the same way as the membrane. This passage of water into the roothairs or through the membrane is called osmosis. Strong solutions of salts as found in salt marshes, alkali soils, and peat bogs interfere with the absorption of moisture by the root-hairs, and in some cases the water is even taken from the roots.