b. c. d.

Is the fruit hard or soft? Draw in the position on which it hung on the tree (X 2) the fruit that is given you. Label main fruit-stalk, winglike attachment, single fruit stalk, fruit.

Answer questions given under 1 (above). 3. The elm fruit or ailanthus fruit.

a. Notice the fruit stalk, the single-celled ovary, the wing about the ovary.

Draw (X 2) one of the above-named fruits. Label fruit-stalk, ovary, wing.

b. c. d. Answer questions given under 1 above.

B. Tufted fruits (or seeds).

1. The clematis, dandelion, thistle, or aster fruit.
a. Find the tiny seed-like ovary, containing a single
seed, and the tuft of hair. Draw (X 2) one of
the fruits. Label ovary, tufts of hair.

b. c. d. Answer questions under A, above.

2. The milkweed fruit and seed.

a. (Optional.) Study Fig. 36. Describe the way the pod

104. Seed dispersal by animals. - Laboratory Study No. 49. Study one or more of the following fruits:

A. Burs and stickers.

1. Cocklebur.

a. Hold one of the fruits between yourself and the
light. Do the hooks all curve toward one end
of the fruit or in several directions?
Notice the two larger projections at one end of the
fruit. These are the styles. Draw (X 2) the
outside of one of the cockleburs, showing
the direction of the hooks.
Label ovary,

hooks, two styles (large prongs at one end of
fruit).

b. Rub one of the cockleburs on a rough surface of your clothing and try to remove it. By what means does it cling to the cloth? How is a cow or other hairy animal adapted to disperse this fruit?

2. Burdock.

a. Each burdock consists of a large number of individual fruits. Hold the burdock to the light. In what directions do the hooks extend? Why is this an advantage in securing the distribution of fruits?

b. Answer questions under 1 b above.

3. Bidens (also called pitchforks or beggar's ticks).
a. Hold the fruit to the light or examine it with a
hand magnifier. In what direction do the
little barbs on the two prongs of the ovary
extend? Why is this an advantage?

Draw (X2) one of the bidens fruits. Label
ovary, prongs, barbs.

b. Answer questions in 1 b above.

B. Fleshy fruits. Suggested as home work.

1. In what ways are the seeds of apples, cherries, and of many other fleshy fruits protected while they are ripening?

2. Many fleshy fruits are dispersed by birds and other animals which are seeking food. How are these animals rewarded for doing this work?

3. How are the seeds of ripe peaches and cherries, for example, protected from injury?

105. Fruits and their classification.

If one were asked to give examples of fruits, one would doubtless give such forms as apples, cherries, and peaches. But it is doubtful if he would think of including among fruits, pea pods, pumpkins, chestnuts, and corn. To the botanist, however, these are

FIG. 37. Lengthwise section of apple fruit, showing seeds attached to a central placenta. (Bailey.)

FIG. 38. Cross section of apple fruit, showing seeds and their coverings which constitute the core.

considered to be just as truly fruits as the forms commonly thought of as fruits. Let us see why such diverse plant products as those just named are all included under the heading of fruits. Technically, a fruit is a ripened ovary and its contents with any other part of the plant that is closely incorporated with it; and since the forms named above are all ripened ovaries containing one or more seeds, it is evident that, strictly speaking, they must be classed with the fruits as much as apples and cherries.

Sometimes the flower contains a number of pistils which form a pulpy mass, such as the raspberries and blackberries

(see Fig. 40); hence each of these so-called berries is composed of a number of separate fruits. Sometimes the end of the stem which bears the pistils becomes pulpy and juicy and the dry pistils are embedded in

its outer surface, as is the case with strawberries (see Fig. 42). In other fruits the ovary may form a hard woody wall, as in the nuts like the chestnut (Fig. 39) and acorn, or the wall may be like a tough paper, as in the pods of peas and locusts (Fig. 43). In still other forms the whole ovary may become fleshy, as in the true berries, such as the cranberry, grape, and tomato. Or we may find a combina

tion of a tough wall and a fleshy interior, as in the pumpkin, squash, and cucumber. In cherries, plums, and peaches the ovary forms two kinds of material, the inner very hard and stone-like and the outer pulpy. In fruits like the corn grain and the wheat kernel the ovary wall is so closely united with the coats of the single seed that these grains are commonly considered as seeds.

FIG. 40. Raspberry fruits. The facts just stated with regard to different kinds of fruits suggest a simple form of classification, based largely on the characteristics of the ovary walls. Thus, for instance, all those fruits, such as bean pods,

FIG. 41.-Flower of the strawberry. (Bailey.)

grains, and nuts, in which the walls are
dry at maturity, are called dry fruits.
Those in which the walls are pulpy
throughout, as in the tomato, are termed
fleshy fruits; and those
which are partly fleshy
and partlystone-like, as
in the cherry and peach,

are called stone fruits. Another scheme for classifying fruits is based upon the fact that some fruits break open when ripe and scatter their seeds,

FIG. 43. Pea pod. (Bailey.)

while others remain

closed.

Straw

berry. (Bailey.)

fruits of the first kind
are the bean, milkweed, and pansy, and
of those that remain closed are cherries,
apples, and grains. Whether or not a fruit
breaks open at maturity depends upon
the character of the ovary wall, and this
in turn determines, as we shall now see,
the method by which its seeds are dis-
persed.

106. Home work on fruits. - Laboratory Study No. 50. (Optional.)

Classify the fruits with which you are familiar in a table like