288 SUMMARY OP CUERENT RESEARCHES RELATING TO 



position of the fossil Calamarieae. He regards them as a very large 

 group, varying widely in some points of structure, of which our 

 modern Equisetacese represent a strongly differentiated type. The 

 Equisetacese are therefore calamites, but it is wrong to speak of the 

 latter as in all cases EquisetaceaB. The leaves only rarely display 

 sheathing coalescence (Equisetites) ; and the spores appear to have been 

 destitute of elaters. The spores are frequently dimorphic. VolJc- 

 mannia and Sphenophyllum, as well as the Lycopodiaceae, the author 

 regards as more nearly related to the true Calamarieae than had pre- 

 viously been supposed. In some cases the stems show a very similar 

 structure to that of Equisetum, in the central cavity, the separate 

 vascular bundles with lacunae, the peculiar course of the bundles, and 

 the silicification ; but in other cases, the structure was widely different. 

 A considerable variety was also displayed in the organs of fructifica- 

 tion ; and on the characters of the fructification he proposes to base 

 the diagnoses of the genera. 



Fructification of Sigillaria.*— M. B. Eenault describes in detail 

 the structure of Sigillaria Menardi, and derives therefrom confirmation 

 of his previous conclusion that the Sigillarise are a transitional group, 

 and may be divided into two families: — the Leiodermariese, or 

 phanerogamic Sigillarise, with smooth bark, nearly allied to the 

 Cycadeae, and the BJiytidolepidse or cryptogamic Sigillarise, with 

 channelled bark, allied to the Isoeteae. 



Algae. 



Protoplasmic Continuity in Seaweeds.f — Continuing his re- 

 searches on this subject, Mr. T. Hick finds that in Laminaria digitata 

 (belonging to the Phaeosporeae) the protoplasts of the cortex are 

 rhizopod-like masses, with pseudopodia spreading in such a manner 

 that the cells of each layer are brought into connection with one 

 another and with those of adjacent layers. Both here and in the 

 cortex continuity is effected by the intervention of sieve-plates ; in 

 the epidermal tissue it was not detected with the same certainty. In 

 Himanihalia lorea (Fucaceae) the same phenomena were observed, 

 though by no means so universally. 



Cystosira barbata.f — Dr. A. Dodel-Port has submitted this 

 seaweed to a careful examination, as a type of the Fucaceae. 



The branching is monopodial. The ultimate branches are the 

 organs of assimilation, and bear also the reproductive organs or 

 receptacles at their youngest solid ends. 



In the stem four distinct parts are to be distinguished : — (1) A 

 central cylinder of fibre-cells ; (2) a layer of thick- walled cells with 

 irregular cavities ; (3) the cortical layer, the cells of which become 

 gradually shorter centrifugally, the outermost being isodiametrical 

 and containing chromatophores ; (4) the epidermis, not sharply 



* Comptes Kendus, ci. (1885) pp. 1176-8. 



t Jonrn. of Bot., xxiii. (188.5) pp. 354-8. Cf. this Journal, v. (1885) p. 682. 

 X Dodel-Port, A., ' Biologisuhe Fra^'mente,' Part I. (10 col. pis.), Cassel and 

 Berlin, 1885, See Bot. Centralbl., xxiv. (1885) p. 129. 



