



424 BOTANICAL GAZETTE [may 



Mesozoic Equisetales. — One great desideratum in discussions as to the origin 

 of existing plants is an increase in our knowledge of those of the Mesozoic. At 

 the present time the Paleozoic flora is much better understood than that of the 

 intervening period, which gave rise to the characteristic groups of our existing 

 flora. A contribution by Halle 16 throws a good deal of light on the organization 

 of the equisetum-like forms of the earlier Mesozoic (Upper Triassic and Lower 

 Jurassic). The author describes the vegetative stems and cones of several Equi- 

 setales. He establishes a new genus, Neocalamites, which has the general habit 

 of the Calamites, including the leaf whorl made up of ununited leaves, with the 

 herbaceous texture of the existing equise turns. It further resembles Calamites 

 in the fact that only every second intemodal strand (or fewer) gives off a leaf 

 trace in the region of the node, and in the fact that the intemodal bundles are 

 frequently continuous at the nodes, in contrast to the alternating condition found 

 in Equisetum. In Equisetites the leaves are in united sheaths as in the living 

 genus, but in some of the species described by the author the same continuous 

 bundles, and leaf traces fewer than the intemodal strands, as are found in the 

 Paleozoic Equisetales, are described. In the smaller branches, however, the leaf 

 strands correspond to the number of intemodal strands, thus foreshadowing the 

 condition found in the living Equisetum. Perhaps the most interesting feature 

 of this important addition to our knowledge is the description of the cones, cone- 

 scales, and spores of Equisetites. The two former do not differ strikingly from 

 those of the living genus, but the spores, interestingly enough, show the absence 

 of elaters and che presence of triradiate sculpture described for the megaspores 

 and microspores of the Calamites. The cones are isosporous. This article con- 

 nects in a very satisfactory way the organization of the Paleozoic Equisetales with 

 that of those still living, and illustrates the important bearing of paleontological 

 facts on any stable scheme of evolution.— E. C. Jeffrey. 



Membrane of diatoms.— Mangin presents 17 an account of some extended 

 observations on the diatoms, especially those of the plankton. His most impor- 

 tant observations relate to the membrane. This he finds to be composed of a 

 substance identical with pectic compounds, combined more or less intimately 

 with silica; the siliceous skeleton thus formed is impregnated and invested with 

 a gelatinous membrane which often hides, at least in plankton species, the charac- 

 teristic ornaments. He controverts the ideas of Schutt as to the growth of the 

 membrane (through agency of an extracellular plasma), which he discusses a 

 some length; and after describing improved methods of staining the membrane 

 (by ruthenium red, and by an old solution of hematoxylin with ammonium- or 

 ruthenium-alum, which may be aged artificially), he gives some detailed exam- 

 ples in the study of certain species.— C. R. B. 



J ' Halle, T. G., Zur Kenntniss des mesozoischen Equisetales Schwedens. Kung. 

 Svensk. Vetenskapsakad. Handl. 43:Xo. i. 1908. 



'7 M angix, L., Observations sur les Diatomees. Ann. Sci. Nat. Bot. IX. : IX 7 

 219- figs. 14. 1908. 



