insect-visited flowers, and discovered in almost every case that showy, sweet-scented, or otherwise attractive flowers were adapted or fitted to be cross-pollinated by insects. He also found that, in the case of flowers that were inconspicuous in appearance, often a compensation appeared in the odor which rendered them attractive to certain insects. The so-called carrion flowers, pollinated by flies, are examples, the odor in this case being like decayed flesh. Other flowers open at night, are white, and provided with a powerful scent so as to attract night-flying moths and other insects. Flowers adapted to be cross-pollinated by insects are frequently irregular in shape. Thus butter and eggs is a flower which is well fitted for cross-pollination by insects.

Butter and Eggs (Linaria linaria). From July to October this very abundant weed may be found especially along roadsides and in sunny fields. The flower cluster forms a tall and conspicuous flower cluster known as a spike, the yellow and orange flowers being arranged so that they come out directly from the main flower stalk.

The corolla projects into a spur on the lower side; an upper two-parted lip shuts down upon a lower three-parted lip. The four stamens are in pairs, two long and two short. (The stamens of two lengths are so placed that they may allow self-pollination in stormy weather, when insects fail to reach the flower. The instructor should explain this.)

Certain parts of the corolla are more brightly colored than the rest of the flower. This color is a guide to insects. Butter and eggs is visited most by bumblebees, which are guided by the orange lip to alight just where they can push their way into the flower. The bee, seeking the nectar secreted in the spur, brushes his head and shoulders against the stamens. Visiting another flower of the cluster, it would be an easy matter accidentally to transfer this pollen to the stigma of another flower. In this way cross-pollination is effected.

Insects as Pollinating Agents.1-No one who sees a hive of bees with their wonderful communal life can fail to see that these insects play a great part in the life of the flowers near the hive. A famous observer named Sir John Lubbock tested bees and wasps to see how many trips they made daily from the hive to the flowers, and found that the wasp went out on 116 visits during a working day of 16 hours, while the bee made but a few less visits, and worked only a little less time than the wasp worked. It is evident that in the course of so many trips to the fields a bee must light on and cross-pollinate many hundreds of flowers.

Study of a Bee. The body of a bee (and of all other insects) is divided into three parts. Attached to the middle part (the

thorax) are three pairs of jointed legs and two pairs of tiny wings. By the legs and the jointed body we are able to distinguish insects

1 Suggestions for Field Work. -At this point, at least one field trip should be introduced for the purpose of studying under natural conditions the cross-pollination of flowers by insects. For suggestions for such a trip, see Hunter and Valentine, Manual, page 207. Many of the following exercises on fall flowers may profitably be taken in the field and reported on by the pupil as class exercises. Excellent suggestions for a field trip may be found in Andrews, Botany All the Year Round. To make such a trip successful, the teacher should first know the locality and should have directions in the hands of each pupil before starting. Flowers which are abundant in the fall and which show adaptations easily worked out by pupils are the evening primrose (Onagra biennis), moth mullein (Verbascum blattaria), and jewel weed (Impatiens biflora).

Directions for work on these forms and for a field trip will be found in the Laboratory Manual, Prob. VII.

from other animals. If we look closely at the bee, we find the body and legs more or less covered with tiny hairs; especially are these hairs found on the legs. When a plant or animal structure is fitted to do a certain kind of work, we say it is adapted to do that work. The joints in the leg of the bee fit it for complicated movements; the arrangement of stiff hairs along the edge of a concavity in one of the joints of the leg forms a structure well fitted to hold pollen. In this way pollen is collected by the bee and taken to the hive to be used as food. But while gathering pollen for itself, the dust is caught on the hairs and other projections on the body or legs and is thus carried from flower to flower. Thus cross-pollination may be effected.

Pollination not intended by the Bee. The cross-pollination of flowers is not planned by the bee; it is simply an incident in the course of the food gathering. The bee visits a large number of flowers of the same species during the course of a single visit from the hive, and it is then that cross-pollination takes place.

Suggestions for Field Work. - In any locality where flowers are abundant, try to answer the following questions: How many bees visit the locality in ten minutes? How many other insects alight on the flowers? Do bees visit flowers of the same kinds in succession, or fly from one flower on a given plant to another on a plant of a different kind? If the bee lights on a flower cluster, does it visit more than one flower in the same cluster? How does a bee alight? Exactly what does the bee do when it alights?

Is Color or Odor in a Flower an Attraction to an Insect? Try to decide whether color or odor has the most effect in attracting bees to flowers. Sir John Lubbock tried an experiment which it would pay a number of careful pupils to repeat. He placed a few drops of honey on glass slips and placed them over papers of various colors. In this way he found that the honeybee, for example, could evidently distinguish different colors. Bees seemed to prefer blue to any other color. Flowers of a yellow or flesh color were preferred by flies. It would be of considerable interest for some student to work out this problem with our native bees and with other insects. Test the keenness of sight in insects by placing a white object (a white golf ball will do) in the grass and see how many insects will alight on it. Try to work out some method by which you can decide whether a given insect is attracted to a flower by odor alone.

The Sight of the Bumblebee.

The large eyes located on the sides of the head are made up of a large number of little units, each of which is considered to be a very simple eye. The large eyes are therefore called

the compound eyes.
simple eyes, or, in most cases, with both.

All insects are provided with compound eyes, with The simple eyes of the bee may be found by a careful observer between and above the compound eyes.

A lily: P, petal; S, stamen (anther); SEP, sepal; St, pistil (stigma). Note the nectar guides on the petals.

One would suppose that with so many eyes the sight of insects would be extremely keen, but such does not seem to be the case. Insects can, as we have already learned, distinguish differences in color at some distance; they can see moving objects, but they do not seem to be able to make out form well. To make up for this, they appear to have an extremely well-developed sense of smell. Insects can distinguish at a great distance odors which to the human nose are indistinguishable. Night-flying insects, especially, find the flowers by the odor rather than by color.

The bee is
This food may

Nectar and Nectar Glands. attracted to a flower for food. consist of pollen or nectar. Nectar is a sugary solution that is formed in the flower by little collections of cells called the nectar glands. The nectar glands are usually so placed that to get to them the insect must first brush the stamens and pistil of the flower. Frequently the location of the nectaries (nectar glands)

is made conspicuous by brightly colored Head of the bumblemarkings on the corolla of the flower. The row of dots seen in the tiger lily is an example.

bee; a, antenna; g, tongue used in licking the nectar from flowers; m, maxillæ.

Mouth Parts of the Bee. The mouth of the bee is adapted to take in the foods we have mentioned, and is used for the purposes for which man would use the hands and fingers. The honeybee laps or sucks nectar from flowers, it chews the pollen, and it uses part of the mouth as a trowel in making the honeycomb. A glance at the Figure shows us that the mouth

parts of the bee are complex. The parts consist of a pair of very small jaws or mandibles, certain other structures, maxilla, part of the lower lip called the labial palps, and

a long tonguelike structure called the ligula. The uses of the mouth parts may be made out by watching a bee on a well-opened flower.

Other Flower Visitors.1 Other insects besides the bee are pollen carriers for flowers. Among the most

useful are moths and but

terflies. Both insects feed

a flower.

only on nectar, which they A humming bird just about to cross-pollinate suck through a long tubelike proboscis. The heads and bodies of these insects are more or less thickly covered with hairs, and the wings are thatched with hairlike, tiny scales. All these structures are of use to the flower

Flies and some other insects are agents in cross-pollination. Humming birds are also active agents in some flowers. Snails are said in rare instances to carry pollen. Man and the domesticated animals undoubtedly frequently pollinate flowers by brushing past them through the fields..

1 If the study of other insects is taken up in the fall in connection with the flower, the student should be referred to parts of Chapters XX and XXI and to the Laboratory Manual.