The Khedivial Agricultural Society of Egypt recently voted a capital expenditure of £2000 towards the establishment of a Mendelian Experiment Station for the study of heredity in cotton.
From studies of the growing cotton plant in Egypt the author was led some years ago to the conclusions that the wall of the cotton-seed hair-cell was “probably composed of concentric layers, laid down during the active growth of each successive night, and numbering about twenty-five in all . . . they would thus, at the most, be about 0∙0004 mm. in depth, so that their resolution by the microscope is highly improbable without some previous treatment.” Various methods were tried with the intention of bringing these layers into the limits of microscopic vision, but it was not until five years later that an accidental observation gave the clue to a method by which the limitations of microscope observation may be extended, and these layers made actually visible. The observations which followed, demonstrating the existence of concentric layers in the wall of the cotton-hair as well as in the “fuzz-hairs,” would have been interesting in any case on account of their bearing on all the physical and chemical problems which this typical cellulose presents. C. F. Cross has insisted on the necessity for considering cellulose problems in terms of “the ultimate fibre," but it now seems probable that the ultimate unit components must be the single layers composing the wall of the said fibre. The bare fact of the existence of such layers would have had no particular significance if it could not have been connected with previous precise study of the growth of cotton-hairs. By counting the number of layers in material previously preserved at known dates during the course of those studies, and remembering the cardinal fact that growth is daily arrested by the sunshine effect under Egyptian conditions, we have been able clearly to show that these layers are actually the growth-rings whose existence we had ventured to postulate. Knowledge of their real existence must materially affect some of our views concerning the physical properties of such hairs.
and Doublers Association, Bollington.) .[P lates 5 and 6.]This analysis of cell-wall structure as seen in cotton hairs began with the inference that diurnal growth rings existed therein. After this inference had been confirmed* it was shown that spiral structures common to all the growth rings were present,j* and that these were of at least two kinds, quick or " pit spirals^ and slow spirals corresponding to objects figured by De Mosenthal. § In our last communication we concluded that these two kinds of spirals might sometimes be independent of one another ; but we now retract this conclusion in the light of results obtained by the improved micro-physical technique which we have substituted for the crude and difficult focussing method formerly employed. In the present communication we propose to study the origin of these spiral structures and to suggest some bearings of our results on problems relating to the molecular structure of cellulose. We abstain at present from extending our studies to comparisons with other plant cells.Before proceeding to the analysis itself we may perhaps mention one side issue of this investigation which affects many calculations about cell-walls. The spiro-fibrillar structure formerly described evidently suggests that the wall is a sponge-like structure with (in the dry state) free air spaces therein. We have ample evidence that this is so, and that the specific gravity of cotton cellulose cell-walls, in their natural condition, is somewhere round 0'90 to 1T0, instead of having the value of 1*55 commonly accepted for the cotton cellulose itself; but the accurate determination of the mean cross-sectional area of the undamaged hair at any fixed temperature and humidity is a matter of
of the National Bank of Egypt. Vol. I. Including all Processes up to the end of Carding. 4j. net. Vol. II. Including the Processes up to the end of Fly-Frames. 4s. net. Vol. III. 10s. net. COTTON MACHINERY SKETCHES. Super Royal 8vo. Sewed. 2s. 6d. COTTON SPINNING CALCULATIONS. IHustrated. Crown 8vo. 4s. net.
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