which together are known as the stigma, and the remainder of the pistil known as the ovary. Describe the pistil of the tulip (and of the trillium) as to position, shape, and color of its parts. 6. Make a drawing twice its natural size of the pistil. Label stigma, ovary.

7. Cut thin cross sections of a well-developed ovary, lay them on a dark-colored background, and study one or more of them with a magnifier to make out the following parts: wall of the ovary, small objects within the ovary known as ovules. (These ovules develop into seeds.) Describe what you have done and tell what you have seen. 8. Make a drawing at least an inch in diameter of a cross section of the ovary, labeling ovary wall and ovules.

9. (Optional.) Make a drawing (corresponding in size to that called for in 6 above) of a lengthwise section of the ovary to show wall of ovary, ovules. Label.

85. Study of the gladiolus flower (autumn study). Laboratory Study No. 42.

Note to the teacher. Be careful to remove each flower close to the central stalk, so that the ovary may not be injured.

A. Parts of the flower.

1. Remove the two leaves at the base of the flower, since these leaf-like organs do not belong to the flower. The outer brightly colored parts of the flower are called the floral envelopes. These colored parts unite to form a greenish tube below.

a. Count and record the number of divisions of which the floral envelopes are composed.

b. State whether or not these divisions are all of the same size.

2. The slender stalks with purple tips, inside the floral envelopes, are called stamens. How many stamens do you find?

3. The single white stalk with three divisions at the top is the upper part of the pistil. The dark green body below the tubular part of the floral envelopes is the lower part of the pistil.

Is the top of the pistil in the flower you are studying lower or higher than the stamens?

4. Make a drawing, natural size, of the side view of the flower, and label the following parts: the divided portion of the floral envelopes, the tubular portion of the floral envelopes, the stamens, the pistil.

B. Essential organs. The stamens and pistils are called the essential organs of flowers because without

them the work of the flower cannot be performed. 1. Carefully slit open the tubular part of the floral envelopes down to the lower part of the pistil. Then remove the floral envelopes, leaving the entire pistil uninjured.

a. State what you have done.

b. To what are the stamens attached?

c. The enlarged part at the top of the stamen is called the anther, the stalk-like part is called the filament. Name and describe the parts of a stamen.

2. Make a drawing, natural size, of a portion of the floral envelope to which a stamen is attached. Label division of floral envelopes, anther, filament.

3. Find a flower the stamens of which have a powdery substance known as pollen. Which part of the stamen produces the pollen?

4. The pistil consists of an enlarged portion at the base called the ovary, a stalk-like portion called the style, and a spreading portion at the top, each part of which is called a stigma. Name and describe each part of the pistil.

5. Make a drawing, natural size, of the pistil and label ovary, style, stigmas.

6. Cut thin cross sections of a well-developed ovary, lay them on a dark-colored background, and study

one or more of them with a magnifier to make

out the following parts: wall of ovary, small objects within the ovary known as ovules. These ovules develop into seeds. Describe what you have done and tell what you have seen.

7. Make a drawing at least an inch in diameter of a cross section of the ovary, labeling ovary wall, ovules.

8. (Optional.) Make a drawing (corresponding in size to that called for in 7 above) of a lengthwise section of the ovary to show wall of ovary, ovules. Label.

86. Pollination.

We have learned in our study of flowers

that pollen is produced in the anther of the stamen, and ovules

FIG. 24.-Structure of a plum blossom. pistils, and to this process is

Rub a small brush or the end of a toothpick over a stamen (e.g. tulip, Easter lily, or gladiolus) which

has an abundance of pollen, and FIG. 25.-A, pollen adhering

then brush this pollen over the surface of the stigma.

to stigma; B, pollen of plum escaping from the anther of a stamen. (Bailey.)

1. Describe what you have done.

2. Examine the surface of the stigma with a magnifier and state what causes the pollen to stick to the stigma.

88. Microscopical Demonstration of Pollen Grains and their Development.-Laboratory Study No. 44. (Optional.) Prepare some sugar solution by adding to ten teaspoonfuls of water one teaspoonful of molasses or grape sugar and heat to boiling point. Put some of this sugar solution in a clean Syracuse watch glass. When the solution has cooled, mix with it some pollen from the flower of a tulip, a trillium, a sweet pea, or nasturtium. Several of these glasses might well be prepared with slightly different strengths of sugar solution and piled one above the other to keep out mold spores. Leave the glasses until the pollen grains have germinated. Study the preparation with the low power of the compound microscope.

1. Find some pollen grains that have not begun to grow tubes. Describe the form of one of the pollen grains.

FIG. 26. Different kinds of pollen grains, highly magnified, two of them forming pollen tubes.- (Duggar.)

2. Find several grains that have formed tubes. What is the color and shape of the tubes?

3. Make a drawing at least a half inch in diameter of a pollen grain before it has sprouted and a drawing of another grain that has sprouted. Label pollen grain, pollen tube.

89. Pollination, germination of pollen grains, and fertilization. We have now learned that pollen by the process of pollination is carried to the stigma of the pistil and adheres to the stigma by a sticky substance which is easily seen on the stigma of the Easter lily and often by hairs, also, as is the case in the tulip and gladiolus. It has been proved that this sticky substance contains sugar which together with other materials furnishes food for the growth of pollen tubes (see 88). As each tube forms, it makes its way down through the stigma and style (if present), and finally reaches an ovule in the ovary. The tip of the tube now penetrates an opening called the micropyle (Greek, micro-small+pula-gateway)

in the ovule. Part of the living substance of the pollen grain now unites with a part of the living substance of the ovule. This union is known as fertilization. After fertilization has taken place the ovule develops into a seed.

90. The cellular nature of pollen and ovules.