The question naturally arose whether the 12-chromosome species would not hybridize with each other. It happened that these crosses had never been attempted, because in these three species no plants had been found whose characteristics were desirable for combination. With the new incentive, however, numerous cross-pollinations were made in 1926 between the Canada blueberry and the dryland blueberry and between the dryland blueberry and the bigbush blueberry. Fruit set promptly, the berries contained an abundance of seeds, and the seeds have now produced vigorous young plants, some of them ready to flower next spring. From still another cross, not yet mentioned, curious results had been obtained. This was a cross, made in 1922, between the rabbiteye blueberry of Florida, Vaccinium virgatum, and one of the large-berried northern hybrids. Many of the pollinations failed, but berries containing seeds were obtained in sufficient number to produce several hundred seedlings. They grew with great vigor and flowered freely, but although hundreds of pollinations were made on them with pollen of known virility, not a single welldeveloped berry resulted, and the occasional small and late berries they bore contained no seed possessing an embryo. In the production of offspring this cross, therefore, has proved completely sterile. Upon examining the rabbiteye blueberry, Dr. Longley found that this species has thirty-six chromosomes. The plant with which it was crossed has twenty-four chromosomes. The resulting sterile hybrids usually have thirty chromosomes. Since many who read this paper are doubtless unfamiliar with the action of the chromosomes, the minute bodies that are reputed to carry to the offspring the characteristics about to be inherited from the two parents, the following brief statement is presented regarding them. It represents the ideas current among geneticists. When the first cross-pollination in this series was made, the thirty-six chromosomes from the pollen grain of one parent were poured into the egg cell of the other parent, which already contained twenty-four chromosomes. The total of sixty chromosomes was carried through each cell of the resulting hybrid, in the ordinary process of cell division, until the plant was nearly ready to flower. Then ensued a phenomenon known as the reduction of the chromosomes, in the cells that produce the pollen grains and the egg cells. Presumably twenty-four of the sixty chromosomes, representing those derived from the 24-chromosome parent, combined with twenty-four of the thirty-six chromosomes representing the other parent. The remaining twelve chromosomes from the second parent, having no chromosomes with which to pair normally, paired abnormally with each other or remained unpaired This abnormal pairing of the chromosomes, according to the current view, caused a derangement of the normal activities of the plant, which resulted in sterility of fruit production. The rabbiteye blueberry has come into cultivation extensively in the South by the transplanting of the wild bushes. It is of great importance that this spe cies be improved by hybridization. The first attempt to do this failed, seemingly because the rabbiteye blueberry stood alone in the number of its chromosomes. The possibility of improvement appeared to depend on the finding of another species having thirty-six chromosomes, and possessing also desirable characteristics that could be transmitted to a hybrid In the higher Appalachian mountains of western North Carolina and eastern Tennessee occurs a native species, Vaccinium pallidum, the Blueridge blueberry, which has large, beautiful and delicious fruit. As early as 1911, attempts were made to cross this with the highbush blueberry and the lowbush blueberry; but all the pollinations failed, and the Blueridge blueberry was therefore abandoned as a breeding stock. In the hope that this blueberry might be a 36chromosome species, because it had failed to hybridize with the 24-chromosome species, plans were made, for the spring of 1927, to determine its chromosome number. Material was obtained from western North Carolina through the courtesy of George E. Murrell, horticulturist of the Southern railway. On critical study of the material Dr. Longley found, to the great delight of all of us, that the Blueridge blueberry has thirty-six chromosomes. If future experience confirms the view that the number of the chromosomes in blueberry species is a true index of the facility of their interbreeding, as the experiments indicate thus far, we shall be able next spring to hybridize the rabbiteye blueberry with the Blueridge blueberry, and thus add one more item to our knowledge of the means by which wild species become plastic in the hands of science. FREDERICK V. COVILLE U. S. DEPARTMENT OF AGRICULTURE CHROMOSOMES IN VACCINIUM A CYTOLOGICAL investigation of the number of chromosomes in a dozen Vaccinium species and hybrids has revealed three diploid, six tetraploid, one pentaploid and two hexaploid forms. The material used for this study of the chromosome in microspore-mother-cells was collected early in the springs of 1924, 1925, 1926 and 1927 from Vaccinium plants grown under the direction of Dr. Frederick V. Coville at the greenhouses of the Bureau of Plant Industry, Washington, D. C., and from plants growing in their wild habitats. Two methods were used in preparing buds for study. In one, the buds were killed with chromoacetic killing fluid, embedded in paraffin and stained with Haedenhains haematoxylin. In the other, fresh collected buds or buds killed in acetic-absolute (1-3) were stained with aceto-carmine killing and staining fluid. The former more tedious method was very satisfactory and served as a check against the latter quicker method, which was found to give excellent preparations when the difficulty of using aceto-carmine on the minute anthers of Vaccinium was overcome. DIPLOID SPECIES Vaccinium atrococcum, wild plant from Aurora Hills, Va. These three species were found to have 12 bivalent chromosomes at diakinesis of the pollen-mother-cell. Since 12 is the lowest number found in any Vaccinium species, it seems probable that 12 is the basic number for the genus, and that the three forms listed are true diploid species. This view is substantiated from our study of Polycodium stamineum and Gaylussacia baccata, representative forms of two closely related genera. The same basic chromosome number, 12, characterizes these two species. The meiotic phases in the pollen-mother-cells of these three species are passed through in a very regular manner, giving each cell of the tetrad the reduced chromosome number. Text figure 1A shows the chromosomes of Vaccinium canadense in the heterotypic prophase. The chromosomes are small compact masses at this phase and show no individual morphological characteristics. TETRAPLOID SPECIES Vaccinium angustifolium, wild plant from Middlesex Fells, Mass. Vaccinium angustifolium, wild plant (Russell). Vaccinium corymbosum, wild plant from Lincoln, Mass. Vaccinium corymbosum, wild plant (Taylor No. 2). Vaccinium corymbosum, wild plant from North Carolina (Sampson). Vaccinium hirsutum, wild plant. Vaccinium corymbosum × V. corymbosum (Dunfee x Rubel, plant No. 20 of culture 2300). Vaccinium angustifolium × V. hirsutum (culture 1560). Vaccinium angustifolium × V. myrsinites (culture 1535). (Vaccinium angustifolium × V. myrsinites) × V. corymbosum (culture 1908). FIG. 1. Microspore-mother-cells of Vaccinium: A, heterotypic prophase in V. canadense, showing spindle and twelve chromosomes; B, diakinesis in V. angustifolium, showing twenty-four bivalent chromosomes; C, homotypic metaphase in V. pallidum, side view of left spindle, end view of right spindle, the latter showing thirty-six chromosomes; D, homotypic metaphase in V. corymbosum × V. virgatum, the plate at the right showing thirty chromosomes. (A, × 800; B, × 800; C, × 600; D, x 500.) The three species and four hybrids listed above were found to have 24 as the reduced or haploid number of chromosomes. The increase from 12 to 24 chromosomes made it more difficult to find cells where chromosome counts could be made. Text figure 1B shows the chromosomes at diakinesis in V. angustifolium (Russell). The chromosomes show to some extent their paired nature at this stage. A few assume such shapes as opened and closed rings but a detailed study of individual chromosome characters was not attempted. HEXAPLOID SPECIES Vaccinium virgatum, wild plant from Crestview, Florida (culture 1881). Vaccinium pallidum, wild plant from Pisgah Ridge, North Carolina. In the spring of 1926 some buds from two plants of V. virgatum were procured. In this species 36 haploid chromosomes were found. The discovery of a hexaploid species led us to extend our search. In the spring of 1927 buds of V. pallidum were procured. Our material gave us only a few well-preserved cells in which the chromosome number could be counted. Fig. 1C pictures the homotypic metaphase of V. pallidum showing 36 chromosomes. Diploid, tetraploid and hexaploid forms all show a regular pairing of chromosomes at diakinesis and abnormalities were very rare in any of the reduction phases. PENTAPLOID HYBRID Vaccinium corymbosum × V. virgatum (Katharine x Rabbiteye). The reduction stages were studied in several F1 plants of the foregoing interspecific hybrid. Each showed abnormalities such as are usually met with in hybrids whose parents had different chromosome numbers. Occasionally all chromosomes were paired, giving bivalent chromosomes at diakinesis. A regular mother-cell is pictured in Fig. 1D, in which there. are 30 chromosomes. More frequently the mother-cells are found to be much vacuolated and the reduction phases irregular, giving as a result polycary, polyspory and very little normal-appearing pollen. A. E. LONGLEY U. S. DEPARTMENT OF AGRICULTURE THE STRETCHING OF COPPER WIRE THE following suggestive experiment has been in use in the Physical Laboratory of Queen's University at Kingston, Ont., for some years. As it is thought to embody some novel features it is offered to those who may be interested in it. A light copper wire is stretched horizontally on an ordinary laboratory stand, as shown in Fig. 1. The depression of its mid-point for various loads is observed through a reading microscope. Stress and strain are expressed in terms of the dimensions of the wire, the load and the depression of the midpoint, and, from the plot of one against the other, values are found for Young's modulus, for the stress or strain at the elastic limit, for the yield point and for the stress and the strain initially in the wire. 4 12 gl 4 л r2 and gives Young's modulus for the copper used. is the elastic limit and C the "yield point." The ariation of the level of the fiducial mark from its iginal position for each of these points is shown 7 the double line on the plot (scale to the right hand plot). It will be observed that the break at E rresponds with the elastic limit at B, and that F where the large yield occurs) corresponds with C a the line of stress and strain. And finally, if one extends the line B A back to THE AMERICAN ASSOCIATION FOR THE ADVANCEMENT OF SCIENCE THE REGULAR FALL MEETING OF THE EXECUTIVE COMMITTEE THE regular fall meeting of the executive committee f the American Association was held at the Urbanaincoln Hotel, in Urbana, Illinois, on Monday, Octoer 17, 1927. Three sessions were held, each of about wo hours, beginning at 10:00, 3:00 and 8: 00 o'clock, nd the members who were present dined together at :15 at the same hotel. The following members were resent: Cattell, Fairchild, Livingston, W. A. Noyes nd Ward. The following items of business were ransacted, with the approval of those present and with the subsequent approval of Dr. Humphreys, who dded his vote to the five votes of those who were resent at the sessions. Each item of business consequently has the approval of a majority of the com mittee and becomes a legal action of the association. The members of the committee who were unable to be present at this meeting are Humphreys, Kellogg, Moulton, A. A. Noyes, Pupin and Wilson. The official minutes of the meeting have now been approved by means of a mail vote. 1. The permanent secretary reported that the minutes of the last preceding meeting had been approved by mail. 2. The permanent secretary read a communication from the treasurer (dated May 12, 1927), calling attention to the will of the late Benjamin Pickman Mann, of Washington, D. C., by which the American Association is to receive the balance of a trust established by the will, after certain provisions have been cared for. 3. The permanent secretary's annual financial report for 1926-27, of September 30, 1927, was accepted and referred to the council. 4. The permanent secretary's proposed budget for the fiscal year 1927-28 was unanimously approved. This is based on prospective receipts (entrance fees of new members and annual dues) of $70,000, of which $43,000 is to be expended for journal subscriptions for members (SCIENCE or The Scientific Monthly). 5. The permanent secretary's annual report on membership for the fiscal year 1926-27 was accepted. On September 30 the total number of members in good standing was 13,930, representing an increase of 537 since the preceding annual report. The total enrolment (including, besides members in good standing, those whose names were retained on the roll although in arrears for one or for two years) was 14,862, representing an increase, since last year's report, of 496, or 3.4 per cent. New members and reinstatements amounted to 1,327 for the fiscal year just closed. The total loss in enrolment amounted to 831, including 178 deaths, 281 resignations and 372 names dropped October 1, 1926, at the close of two years of arrears. On October 1, 1927, 412 names were dropped from the roll on account of two years of arrearage. The permanent secretary added that 450 new members had been enrolled since September 30, 1927. (This number has now increased, November 14, 1927, to 1,114 and the total enrolment is now 15,572.) 6. The permanent secretary reported that $1,310.00 had been received as contributions from members to the Agassiz Bust Fund (see SCIENCE for December 10, 1926) and that that amount had been paid over to the Hall of Fame, New York University. The expenses of the committee on the Agassiz Bust Fund were $362.33, met from the current funds of the permanent secretary's office and not charged against the fund. This report was approved and the permanent secretary was asked to make arrangements, if possible, by which a photograph of the Agassiz bust, when it is unveiled, may be published in The Scientific Monthly and copies of the picture may be sent to all contributors to the fund. (Work on the bust is now in progress.) 7. Dr. Ward presented a report for the special committee on academy relations and in response to this report the executive committee took action as indicated in paragraphs 8-12 below. 8. The executive committee recognized the newly formed Colorado-Wyoming Academy of Science, which will hold its first meeting at Laramie, November 25 to 26, 1927, and recommended to the council that this academy be affiliated with the association. The region of the academy is Colorado and Wyoming. 9. It was voted that the special committee on acad-` emy relations consist of the representatives of the affiliated academies in the council (one from each affiliated academy), together with all members of the committee on inter-academy relations that was appointed by the academy conference at Philadelphia and three members representing the executive committee of the association (Ward, Cattell, Livingston). Dr. Ward is chairman. 10. It was voted that a session of the committee on academy relations be arranged to occur immediately following the first council session at Nashville, on the afternoon of Monday, December 26. 11. The permanent secretary was asked to arrange a complimentary dinner of the committee on academy relations, to be paid for out of the current funds of his office, for the evening of Monday, December 26, following the committee session and preceding the opening session of the Nashville meeting. The permanent secretary was asked to invite Dr. Wilhelm Segerblom, recently president of the New Hampshire Academy of Science, to be a guest of the committee for the session and for the dinner, requesting that he take part in the discussions. Dr. Segerblom has made a study of the state academies of sciences and gave some of his results in his retiring presidential address before the New Hampshire Academy at Waterville, N. H., on June 4, 1927. His address is soon to appear in SCIENCE. 12. The official affiliation of the Society for Experimental Biology and Medicine was ratified. The society has 784 members, of whom 390 are fellows of the association. It is to have two representatives in the association council. 13. The official affiliation of the South Carolina Academy of Science was ratified. The academy has 54 members, of whom 18 are now members of the association. 14. One hundred and seventy-two fellows were elected, distributed among the sections as follows: 15. The rules for the award of the American Association prize of $1,000 were reviewed and it was voted that the Nashville award is to be made according to the rules followed at the fifth Philadelphis meeting. These rules were published in SCIENCE for December 2. 16. The executive committee made an appropriatios of $100, from the treasurer's funds, to aid the work of the National Conference on Outdoor Recreation. 17. A request was considered, from the mayor of Southwark, for a financial contribution to the Farday Memorial Collection, kept in the Central Reference Library, Southwark, London, and the permanet: secretary was asked to inform the mayor that the association has no funds that might be employed in this way but that it highly approves of the Faraday Memorial Collection. Through its official journal, SciENCE, the association will be glad to give publicity among American scientists to a letter or note on this subject that may be sent to the permanent secretary. 18. Evening and afternoon lectures of a non-technical nature were approved for the Nashville meeting, as these may be arranged by the permanent secretary. 19. The executive committee approved the plan o having at the Nashville meeting a lecture by a British scientist if that can be arranged. 20. The following resolution was adopted: Resolved, That the American Association, as one of the sponsor organizations for this project, approves the list of standardized mathematical and engineering symbols referred to in SCIENCE for August 12 and September 9, 1927. The list has been published in full in the Journal of Engineering Education for June, 1927; the Journal of the Society of Automotiv Engineers for July, 1927, and Mechanical Engineer ing for August, 1927. 21. Dr. Fairchild presented an invitation from the president of the University of Rochester, requesting that the annual meeting of December, 1933, be held at Rochester, N. Y. This invitation was tentatively accepted, pending detailed arrangements. 22. The executive committee adjourned to meet s the Andrew Jackson Hotel in Nashville at 10:00 o'clock on Monday, December 26, 1927. BURTON E. LIVINGSTON, Permanent Secretary |