118 Physiologie. — Algae. 



mary cylinder. The bundles represent fragmented concentric structures 

 and may be regarded as an ancestral remnant of the innermost 

 cylinder in certain MediiUoseae. The inversly orientated Strands 

 occurring on the dorsal side of the bundles of peduncles and sporo- 

 phylls are the remains of steles in which the dorsal side has become 

 completely aborted. They thus form remains of a second cylinder. 

 All vascular cylinders or rings of Cycads are to be regarded as 

 mutually homologous, whether primary or secondary. In certain 

 Medulloseae the outer part of the secondary xylem of the primary 

 cylinder far exceeds in thickness the inner portion; in all modern 

 Cycads the inner portion is entirely extinct. In the cotyledonaiy 

 node of Cycas siameiisis a number of concentric steles occur outside 

 the root stele and these are found in several genera. 



Rudimentary inverted Strands occur on the inner side of the 

 third and fourth extrafascicular cylinders of Macrosaniia Fraseri 

 representing portions of concentric Strands such as occur outside 

 the central cylinder of M. Denisonii. In Cycas Seernanni the first 

 extrafascicular ring consists of concentric Strands. The cauline colla- 

 teral bundles of Cycas correspond to these and also to the „accessory 

 Strands" of Medullosa anglica. The evidence is in favour of the 

 derivation of both the primary and secondary rings of Cycadean 

 Stern Organs from the polystelic or solenostelic structure of the same 

 Organs in the Medulloseae. 



b) Origin of Foliar Structures. The leaf trace bundles of modern 

 Cycads are homologous with the concentric leaf trace bundles of 

 the Mediillosae. In the peduncle of Starigeria some of the sporophyll 

 traces consist of three small separate bundles, grouped around a 

 common centre and thus representing a concentric bündle; concentric 

 sporophyll traces also occur. In the peduncle oi Encephalartosvillosus 

 the leaf traces leave the cylinder in groups each of which may be 

 regarded as equivalent to a Single concentric leaf trace oi Medidlosa. 

 The Single concentric petiolar bündle of Lyginodendron maj^ be 

 regarded as the equivalent of a number of collateral bundles united 

 by their centripetal xylems, their phloems also fusing and sur- 

 rounding the whole, such as occur in the petiole of Myeloxyloii and 

 Encephalartos. Such fusion has been described in a partial State in 

 E. horridus and Stangeria paradoxa. 



The cones are regarded as the final result of extreme reduction 

 of complex sporophylls of te Neuropterid type where the sporangia 

 were borne as terminal organs; this terminal position is still found 

 in the female sporophyll of Cycas. Two integuments are probably 

 present and are intimately concrescent, giving the appearance of a 

 Single organ. M, Wilson (Glasgow). 



De Gasparis, A., Le alghe delle argille pleistoceniche di 

 Taranto. (Atti Acc. Sc. fis. mat. Napoli. Vol. XII. S. II. N°. 4. 

 (1905). p. 1). 



Les algues que l'A. a trouve dans les argiles pleistoceniques de 

 Taranto se rapportent aux Confervacees, Sifonees, Laminariees, Gon- 

 gilospermees , Nematospermees, Ormospermees et Desmiospermees, 

 avec les especes suivantes: Chaetontorpha c ra ssa (Ag.) Ktz. {}) , Codium 

 tonientosuni Ag., Dictyota dichotonia (Huds.) Lamx. , Callithanmion 

 gramdatum (Duchez), Grateloupia füicina (Wulf) Ag., G. Bassaini n. 

 sp., Diidresnaya coccbiea (Ag.) Bonnern., Delesseria crispa Zanard. et 

 Gelidnini cor^ieuin (Huds.). L. Pampaloni. 



