A Branched Cone of Equisetum, 113

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1 A Branched Cone of Equisetum, E. C. Jeffrey. " The Development, Structure and Affinities of the genus Equisetum." Memoirs of the Boston Society of Natural History, Vol. V., No. 5, R. Kidston. " On the Affinities of the genus I'othoeites, Patterson." Annals and Magazine of Natural History, Series V., Voi: II., O. Lignier. *'Sphenophyllales et Equis^tales, leur origine fllicin^enne commune." Bulletin de la Society Linne^nne de Normandie, Series V., Vol. VII., H. Potoni($, " Lehrbuch der PHanzenpalaontolgie, mit besonderer Rackslcht auf die Bediirfnisse des Geologen," ,, " Die Calamariaceen " and "Die Protocalamariaceen." Die Natiirliche Pflanzenfamilien, edited by Engler and Prantl. Theil I., Unterabtheilung IV. 11. R. Sadebeck. " Equisetaceen (der Jetztwelt)" Die Natiirliche Pflanzenflamilien, edited by Engler & Prantl, Theil I., Unterabtheilung IV. 12. D. H. Scott. Studies in Fossil Botany," ,, " On a Primitive Type of Structure in Calamites." Report of the British Association, Glasgow, " The Old Wood and the New." New Phytologist, ,, " The Present Position of Palaeozoic Botany." Progressus Rei Botanicae. Band I., Heft I., A. C. Seward. " Fossil Plants," Vol. I., H. zu Solms-Laubach. " Fossil Botany," English edition, M. G. Sykes. "The Anatomy and Morphology of Tmesipteris." Annals of Botany, NOTES PROM THE CAMBRIDGE BOTANY SCHOOL. III. ON A BRANCHED CONE OF Equisetum maximum. Lam. [TBXT-PIGS 19, 20J. BY W. STILES, Scholar of Emmanuel College, Cambridge. SPECIMENS of Equisetum in which branching of the strobilus has taken place are not infrequently met with, and have been referred to by various writers from time to time.* In view of the possibility that such abnormal types of structure may shed some light on morphological problems, the structure of a cone of E. maximum, grown in the Cambridge Botanic Garden, ' Milde, J. Nova Act. Acad. Caes. Leop. Carol., Vol. XXVI., l'art 2, p. 412, Duval-Jouve, J. Histoire Naturelle des Equisetum de France, p. 152, Paris, Luerssen, C. in Rabenhorst's Kryptogamen Flora III., p. 683, Leipzig, 1889.

2 114 W. Stiles. and in which branching of tbe strobilus had occurred, was thought worth recording. Before removal of the scale-leaves the strobilus in question appeared to be of normal size. On removal of the scales four smaller cones were found to arise slightly above tbe middle of the chief cone (Fig. 19, A and B). Fig. 19. ^ Branched cone of Equiseium maximum. A. Before removal of scales. B. After removal of scales, x f Tbe internal structure of tbe single specimen was investigated by means of transverse sections only. As stated by Professor Bower,* tbe metbod of brancbing of tbe strobilus is fundamentally dicbotomous and quite different from tbat exbibited in tbe formation of lateral branches. In this cone tbe stele of one of tbe side brancbes is nearly of the same size as tbat of tbe main axis, the other three brancbes being mucb smaller. At tbe base of tbe cone tbe stucture is of the normal type. The first sign of bifurcation of tbe axis is a broadening of tbe stele in one direction. Tbe broadened stele tben becomes constricted at a point on tbe longer diameter. Tbe two parts of tbe stele on either side of tbis point tben become more and more cylindrical by the closing togetber of opposite sides of tbe stele at tbe constriction. Finally, tbe two cylinders close up so tbat eacb brancb of tbe bifurcation bas its own stele. Tbe most interesting feature of tbe cone is tbe presence of vascular bundles in tbe pitb of tbe main axis. Tbese bundles end blindly in the downward as well as in the upward direction, but sbew a tendency to brancb among tbemselves. Tbey are quite unconnected witb tbe ring of normal vascular tissue. Tbe number of bundles in any one transverse section never exceeds tbree, and Bower. Origin of a Land Flora, p. 682, London, B

3 On a Branched Cone of Equisetum maximum. 115 hese appear to be arranged as portions of a ring as indicated in Fig. 20 A. D Fig. 20. A, Diagram shewing the position of the medullary strands.^ r, normal ring of bundles; m, medullary strands; B, C, D, Transverse sections of bundles in the pith, x 100. e, side of the bundle towards the periphery of the cone ; «', side of the bundle towards the centre of the cone cone; t, tracheids ; a, thick-walled parenchymatous cells on the outside of some of the bundles. Fig. 20c shews the appearance usually presented by these medullary bundles in transverse section. They are generally more or less circular and consist of a few tracheids (Fig. 20c, t) scattered irregularly among small-celled parenchyma. On the inner side they pass gradually into the ground-tissue of the pith, but the side towards the periphery of the stem is generally bordered by some thick-walled parenchymatous cells (Fig. 20c, a). No evident phloem could be made out.

4 116 A Branched Cone of Equisetum. Pig. 20B Bhew8 a section of a bundle near its uppermost limit. Pig. 20o represents a section of a bundle just before dying out in the downward direction. At the British Association meeting of 1901, Mr. Gwynne- Vaughan' shewed that the so-called vascular bundle of Bquisetum consists of three strands; a carinal strand, part of which passes out as a leaf-trace, and two lateral cauline strands. He also found that whereas the xylem of the carinal strand is mostly or wholly centrifugal in its development, that of the lateral strands shews indications of having been formed centripetally. He came to the conclusion that the stele of Equisetum was in all probability originally protostelic and that the lateral cauline strands represent the remnants of a former large development of centripetal wood. The discovery made by Dr. Scott,' announced at the same meeting, of centripetal wood in the stem of Calamites petiycurensis lent support to this view. It is perhaps possible, as Professor Seward suggested to me, that the bundles in the pith of the branched cone of Bquisetum may be the remnants of the solid central stele of the ancestors of the living species of Equisetum. Since these bundles are quite unconnected with the normal ring of vascular tissue they are evidently not formed by the branching of normal strands. Moreover, their structure is different from that of the normal bundle, their resemblance being rather to a simple protostele than to anything else. Having regard to these two facts, together with the probable absence of phloem from the medullary vascular strands, and bearing in mind that it is in the reproductive parts of plants that pre-existing structures are likely to occur, it would seem quite possible that the medullary strands in question are the remains of a primitive solid central mass of centripetal xylem. > Gwynne-Vaughan. Brit. Ass. Rep., 1901 ; Annals of Botany, Vol. XV., p 774, See also Bower, Origin of a Land Flora, p. 388, ' Scott. Brit. A8S. Rep, 1901 ; Annals of Botany, Vol. XV,, p. 773, 1901.

NOTES ON GINKGO BILOBA'

NOTES ON GINKGO BILOBA' WALTER WV. TUPPER (WITH PLATE xx) Among the gymnosperms, one of the groups most interesting from a morphological standpoint is the Ginkgoales, the only living representative of