SPIRAL ARRANGEMENTS IN PLANTS 



21 



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Fig. 13. 



Fig. 12. — A, B, C, D. Spiral fronds of an actively growing fern. Drawn natural sizu by 0. Berjeau from a fresh specimen 

 collected by the Author. Shows right and left-handed spirals. 



Fig. 13. — A spiral Chrysanthemum. Drawn from nature for the present work by C. Berjeau. Displays a left-handed spiral 

 arrangement as seen in spiral nebulas (Plate viii.), spiral seeds (Fig. 1], D, E), spiral spermatozoon (Plate xii., Fig. 1, E), spiral 

 shell (Plate xiii., F, G), and the spiral apex of the heart (Plate xvii., Fig. 3, A). 



Fig. 16. 



Figs. 14, 15, and 16 illustrate the spiral arrangements in leaves, flowers, and fruit ; in cells and seeds 

 vessels, climbing plants, &c. 



in 



Fig. 14. — A. " Transverse section of a revolute leaf. The two edges are rolled outwards or away from the axis. 

 B. " Transverse section of an involute leaf. The two edges are rolled inwards or towards the axis. 

 ;■ C. " Transverse section of a convolute leaf. The leaf is rolled upon itself so as to form a continuous coil. 



D. "Transverse section of a plicate or plaited leaf. The parte of the leaf are folded together like a fan. 



E. " Circinate vernation, in which the leaf is rolled up from apex to base, like a crosier. 



F. " Diagram to illustrate contorted or twisted restivation, in which the parts of the whorl are overlapped by each other in turn, 

 and are twisted on their axes as in the mallows. 



G. " Diagram of the flower of the Sowbread (Gydamen) showing the five sepals overlapping each other, and five petals arranged 

 in a contortive manner, five stamens, and the pistil in the centre" (Professor J. Hutton Balfour). 



Fig. 15. — A. " Spiral cell, or cell with a si)iral fibre inside, from an orchid. 



B. " Spiral vessels taken from the melon, showing the elastic fibres uncoiled. 



C. " Vertical section of the seed of Bunias, with its spiral embryo. The cotyledons are rolled upon the radicle in a spiral manner, 

 hence the name spirolobex. 



D. " Exogenous stem, surrounded by a woody climbing plant (Bush rope) which causes contractions and swellings of the stem. 



E. "A stem with alternate spiral "leaves arranged in a ([uincuncial manner. The sixth leaf is directly above the first, and 

 commences the second spiral cycle " (Professor J. Hutton Balfour). 



Fig. 16.— Spiral fruit of Helideres Isora. Forms right-handed spiral (after Baillon). 



