. On the relation of phyllotaxis to mechanical laws. Phyllotaxis; Leaves. MULTIJUGATE TYPES. 187 system is often very marked. (Dianthus, Phlomis (fig. 73), Urtica, etc.) These irregularities in petiole formation, etc., might evidently occur to an equal extent in asymmetrical systems, but they would. Fig. 71. âEpiloliv/m a/ngustifolium, L.âI., section some distance above the apex of a perennating shoot. II., section exactly at the apex, symmetiioal (2 + 2) system. not be so readily noticed, owing to the difficulty of judging the error of such constructions by the eye alone.* * If two equal and
. On the relation of phyllotaxis to mechanical laws. Phyllotaxis; Leaves. MULTIJUGATE TYPES. 187 system is often very marked. (Dianthus, Phlomis (fig. 73), Urtica, etc.) These irregularities in petiole formation, etc., might evidently occur to an equal extent in asymmetrical systems, but they would. Fig. 71. âEpiloliv/m a/ngustifolium, L.âI., section some distance above the apex of a perennating shoot. II., section exactly at the apex, symmetiioal (2 + 2) system. not be so readily noticed, owing to the difficulty of judging the error of such constructions by the eye alone.* * If two equal and similar leaf-primordia meet around an axis and tend to pack, the chances are that, if the ends are â well developed and rounded, one will slip under the other on one side and over the other on the opposite side. The two developing members thus become pushed askew with regard to their true position and that of adjacent members, and an irregular effect is produced. To test true symmetry (2 + 2) as opposed to bijugate (2 + 4) construction, it is necessary to cut the primordia at the apex before they commence to overlap (fig. 71, 2). Again, such secondary confusion will be greater in a symmetrical construction where the primordia of the same whorl should exactly meet, since in the case of asymmetry the paths for slipping are provided in the spiral con- struction. Hence a symmetrical system tends to give greater secondary irregu- larity than an asymmetrical one, and it is thus rather the exception than the rule fo: a decussate plant to show four strict orthostichies. The externally visible. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Church, A. H. (Arthur Harry), 1865-1937; Church, Arthur Henry, Notes on phyllotaxis. London, Williams & Norgate
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