The cell in development and inheritance . urface {anticlines^ or parallel to it {periclines). Ideal schemes ofdivision may thus be constructed for various geometrical figures. Ina flat circular disc, for example, the anticlinal planes pass throughthe radii; the periclines are circles concentric with the periphery. Ifthe disc be elongated to form an ellipse, the periclines also becomeellipses, while the anticlines are converted into hyperbolas confocalwith the periclines. If it have the form of a parabola, the periclinesand anticlines form two systems of confocal parabolas intersecting atright
The cell in development and inheritance . urface {anticlines^ or parallel to it {periclines). Ideal schemes ofdivision may thus be constructed for various geometrical figures. Ina flat circular disc, for example, the anticlinal planes pass throughthe radii; the periclines are circles concentric with the periphery. Ifthe disc be elongated to form an ellipse, the periclines also becomeellipses, while the anticlines are converted into hyperbolas confocalwith the periclines. If it have the form of a parabola, the periclinesand anticlines form two systems of confocal parabolas intersecting atright angles. All these schemes are mutatis mutandis, directly con-vertible into the corresponding solid forms in three dimensions. GEOMETRICAL RELATIONS OF CLEAVAGE-FORMS 363 Sachs has shown in the most beautiful manner that all the aboveideal types are closely approximated in nature, and Rauber has appliedthe same principle to the cleavage of animal-cells. The discoid orspheroid form is more or less nearly realized in the thalloid growths of. Fig. 168. — Geometrical relations of cleavage-planes in growing plant-tissues. [From Sachs,after various authors.] A. Flat ellipsoidal germ-disc of Melobesia (Rosanoff) ; nearly tv-pical relation of ellipticpericlines and hyperbolic anticlines. B. C. Apical view of terminal knob on epidermal hair ofPinguicola. B. shows the ellipsoid type, C. the circular (spherical type), somewhat modified(only anticlines present). D. Growing point of Salvinia (Pringsheim), typical ellipsoid type;the single pericline is, however, incomplete. E. Growing point of Azolla (Strasburger) ; circularor spheroidal type transitional to ellipsoidal. F. Root-cap of Eqiiisitiim (Niigeli and Leitgeb) ;modified circular type. G. Cross-section of leaf-vein, Trichomaiies (PrantI); ellipsoidal type withincomplete periclines. H. Embryo of Alisma : typical ellipsoid type, pericline incomplete onlyat lower side. /. Growing point of bud of the pine {Abies) ; typical paraboloid ty
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectcells, bookyear1902
