constantly. The individuals of any race vary much among themselves, but these differences are matters of growth and environment, and are not inherited. What is produced in reproduction depends on the fundamental constitution of the race, not on the peculiarities of the individual parent. The fundamental constitution of the race is resistant to all sorts of influences; it changes only in excessively rare instances, and for unknown causes; in a study of thousands of individuals of Paramecium, through hundreds of generations, hardly a single case of such change was observed.12 Most differences between individuals are purely temporary and without significance in inheritance; the others are permanent diversities between constant races. Systematic and continued selection is without effect in a pure race, and in a mixture of races its effect consists in isolating the existing races, not in producing anything new.

To give in brief an account of the general results of extensive work, it is necessary to make definite statements, and to omit conditions, exceptions and qualifications. This the reader is asked to remember; the details may be found in the original papers. The results are

based on study and measurements of more than 10,000 individuals of Paramecium, kept under experimental conditions for many generations. But science is essentially incomplete and its results at any time are not final. The author expects to make strenuous attempts to overthrow the generality of some of the results set forth.

12 A single doubtful case is described in the first of the author's two papers: certain individuals of a race acquired a hereditary tendency to remain united after fission, while others did not show this tendency, or showed it less strongly.

THE COLOR SENSE OF THE HONEY-BEE: IS CONSPICUOUSNESS AN ADVANTAGE TO FLOWERS?

JOHN H. LOVELL

IN 1895, Professor Felix Plateau, of the University of Ghent, began the publication of a long series of papers, in which he asserted that Hermann Müller, in formulating his theory of the evolution and use of floral colors, had been misled by a too vivid imagination; and that anthophilous insects are attracted chiefly by odor. In a list of his papers prepared by himself and now before me Plateau states that his latest contribution, entitled Les insects et la couleur des fleurs,1 contains a "summary of the whole." The conclusions of many years of patient research are given at the close of this paper as follows:

"In the relations between the insect fertilizers and entomophilous flowers, the more or less bright coloration of the floral organs has not the preponderating rôle which Sprengel, H. Müller and their numerous adherents have attributed to them. All the flowers in nature might be as green as the leaves without their fertilization being compromised. The sense of smell so well developed among most insects far from being a secondary factor is probably the principal sense which discovers to them the flowers containing pollen and nectar."

By fertilization Plateau doubtless means pollination, for fertilization is an entirely distinct phenomenon, often not occurring until many months after the pollen has been placed upon the stigma. Plateau's conclusions have not met with general acceptance; and in some instances, as he himself naïvely remarks, have been criticized in a "merciless manner."

Floracology is, however, greatly indebted to him not only for many very interesting observations and experi

1

1 Plateau, F. Les insects et la couleur des fleurs. L'Année Psychologique, 13, 67-79, 1907.

ments, but also for insisting that the whole subject of the relations of insects to the colors of flowers should be reexamined and tested experimentally. With the exception of the criticisms of Bonnier, in 1879, Müller's doctrine had remained unquestioned, for no other theory of the significance of brilliant floral leaves is so satisfactory as that they serve as signals or flags to attract the attention of anthophilous visitors. It is well to recall that the great authority, which has been attached to the name of Müller, rests on innumerable observations and collections, which were continued up to the morning of his sudden death from a pulmonary complaint while studying the flowers of the Tyrol. He is still justly regarded as the foremost of florœcologists. Says his biographer Ludwig:

66 He is not dead, he lives and will live so long as a flower enraptures the eye of an investigator. His bright spirit will live on and, we hope, like that of his teacher and friend Darwin long be a light on the way to truth in the heart of nature."

Plateau's first paper dealt chiefly with the concealment of the flowers of the dahlia with green leaves; and his second, which appeared in the following year, with the removal of petals. In the last-named communication he describes how he removed the larger part of the corolla of Digitalis purpurea, Lobelia erinus, Enothera biennis, Ipomoea purpurea, Delphinium ajacis, and Antirrhinum majus; and with the exception of A. majus found that the inconspicuous stumps were visited by insects almost as frequently as the unmutilated flowers. He, therefore, concluded that neither the color nor the form was important, and that insects were attracted by the fragrance alone. I shall again refer to these experiments after relating my own, which gave very decisive results diametrically opposed to those of Plateau.

2

Ludwig, F. Das Leben und Wirken Professor Dr. Hermann Müller's. Botanisches Centralblatt, 17, 404, 1884.

3 Plateau, F. Comment les fleurs attirent les insects, II. Bul. Acad. roy., Bruxelles, 32, 504-34, 1896. I have not been able to obtain this paper, the reprints being exhausted. The experiments are described, apparently with sufficient detail, in Knuth's Handbook of Flower Pollination, and it is upon this account that I have depended.

To determine the influence of the petals of the common pear, Pyrus communis, upon the visits of the honey-bee, Apis mellifera L., a medium-sized tree in full bloom was selected for observation. The day was clear, warm and calm, the bees were numerous and no other insects were present.

A cluster of seven blossoms near the end of a branch was watched for fifteen minutes and received eight visits of the honeybee. The petals were now all removed and it was observed for a second quarter of an hour. Though a number of bees flew near by, it received not a single visit. During a third fifteen minutes there were two visits, due in part to association, for the bees came from other blossoms on the same tree, which had proved the first source of attraction.

Two other clusters of flowers, growing side by side but nearer the bole of the tree, consisting each of eight flowers, were observed for fifteen minutes and sixteen separate visits of the honeybee were noted The petals of one of these clusters were now removed. During fifteen minutes the adjacent cluster, which still retained its petals, received eleven visits, while not one was made to the cluster without petals. In one instance a bee hovered over it but did not alight.

These results were much more conclusive than I had expected; for, in the second experience, it might have been supposed that the odor exhaled by the evaporating nectar of the denuded blossoms would have attracted the bees, which were only an inch or two distant; but their movements were evidently determined almost entirely by the presence of the petals.

On a warm pleasant morning in August at 11:30 o'clock, (A.M., I selected for experiment two groups of flowers belonging to Borago officinalis, or the common borage. They were distant apart about six inches; one contained five flowers; the other, which was at a little higher elevation, contained four flowers. They were both watched for ten minutes. The first received fifteen visits from

the honey-bee, the second thirteen visits. The location of my apiary not far away furnished a large and continuous supply of visitors. The rotate corollas, together with the cone of black anthers, the stamens being attached to the base of the petals, were now removed from the five flowers of the first group. There remained the green calyx, the pistil, and the green disc surrounding it which secretes the nectar. The two groups were now observed for a second ten minutes, the first received no visits, the second seven visits from the domestic bee as previously. Once

a bee hovered around the denuded flowers of the first group but failed to alight. The much smaller number of visits made to group number two during the second interval may in part have been due to the less conspicuousness of the whole patch of flowers. There were scattered upon the ground many partially withered corollas and twice a bee was seen to fly down toward them. With a lens of twenty diameters I examined three of the defoliated blossoms and in two of them found eight or nine small drops of nectar, so that had a bee alighted upon them it would have been richly rewarded for its discernment. The flowers possessed no perceptible odor. Three points in the second part of this experiment should be carefully noted; first, that the flowers from which the corollas had been removed, though they contained an abundance of nectar, received no visits; second, that the flowers left complete received a much less number of visits than during the first interval; third, that the bees were attracted by the wilting corollas lying upon the ground.

On August 14, I made the following experiment upon a staminate flower of the garden squash, Cucurbita maxima. The weather was clear and warm. During an observation of ten minutes it received twelve visits, eight of which were made by honey-bees and four by workers of Bombus terricola Kirby. The perianth was then removed close to the cup-shaped reservoir, but the denuded flower with its prominent club of stamens and yellowish disc was still