ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 773 



Deposition of Calcareous Incrustations on Fresh-water Plants.*— 

 Herr N. Pringsheim maintains that the deposition of a calcareous 

 incrustation on plants growing in fresh water is necessarily connected 

 with the process of assimilation, and takes place only in the light. This 

 can be shown by experimenting on Chara, Nitella, Confervaceas, the 

 leaves of some mosses (Mnium) or aquatic flowering plants, with a satu- 

 rated solution of calcium bicarbonate. The lime-salt used is by no 

 means indifferent, no precipitation taking place from neutral calcium 

 carbonate. The deposition is accompanied by the evolution of bubbles 

 of oxygen, and is evidently a function dependent on transpiration. 



Action of Ether on Plant-life.f — Dr. G. Brenstein finds that an 

 atmosphere saturated with ether kills barley and wheat sprouts within 

 thirty minutes. Five minutes' exposure affected the plants, the tips of 

 the leaves, consequently the oldest portions, being first killed, whilst the 

 basal portions of the leaves, and therefore the youngest parts, resisted 

 longest. Experiments made with portions of Elodea canadensis showed 

 that five minutes' exposure to the ether atmosphere sufficed to kill the 

 plant ; the thin texture of the leaf of this plant seems to make it more 

 permeable to ether than are the leaves of wheat and barley. 



B. CRYPTOGAMIA. 



Cryptogamia Vascularia. 



Systematic Position of Isoetes.:{: — Dr. S. H. Vines points out the 

 objections to the position now generally assigned to the Isoetese — that 

 proposed by Sachs and Goebel, according to which they, together with 

 the Selaginellacese, make up the class Ligulatse. He suggests, on the 

 other hand, that they are a heterosporous form — and the only one 

 hitherto recognized as such — of the Eusporangiate Filicinte. In its 

 general habit, and in the absence of sporangiferous cones and of specially 

 differentiated sporophylls, Isoetes resembles Filices, as also in the more 

 general features of its embryogeny. The velum of Isoetes may also be 

 homologous with the indusium of many Filices. 



Development of the Root of Equisetum.§ — Mr. J. E. Vaizey has 

 investigated the origin of the double endoderm of the root of Equisetum. 

 He finds that the apical cell gives rise to two kinds of tissue, the outer 

 layer or cylinder constituting the exomeristem, which incloses the 

 central cord constituting the endomeristem of Eussow. The exomeri- 

 stem is distinguished from first to last by its cells being arranged in 

 radial rows, while those of the endomeristem are not so arranged, and 

 are smaller than those of the exomeristem. 



Muscineae. 



Reproduction of Thamnium alopecurum.[| — Herr J. B. Schnetzler 

 describes specimens of Thamnium alopecurum, which were fructifying 

 freely, and the sporanges filled with well-developed spores. The author 

 placed the moss under water ; it continued to grow all the winter, and 



* Pringsheim's Jalirb. f. Wiss. Bot., xix. (1888) pp. 138-54. 

 t Arch. Pharm., xxv. pp. 918-24. Cf. Journ. Cliem. Soc. Lond., 1888, Abstr., 

 p. 624. 



X Ann. of Bot., ii. (1888) pp. 117-23. § Ibid., pp. 123-4. 



11 Bull. Soc. Yaud. Sci. Nat., xxiii. (1888) pp. 161-1. 

 ■ 1888. 3 G 



