June i, 1893 J 



NATURE 



109 



forenoons may occasion large evaporation. Tiie transpiration 

 in a forenoon hoar was, in general, four to twelve times that 

 in an afternoon hour ; sometimes as much as twenty or thirty 

 times. The forenoon hours are by far the most favourable to 

 assimilation, and it is most important to the plant that its 

 turgescence be not then too much depressed, an end accom- 

 plished through those water reservoirs. 



The last issue of the memoirs of the Novorossian (Odessa) 

 Society of Naturalists (vol. xvii. 3) consists of a very elaborate 

 work in French, " Monographic des Turbellaries de la Mer 

 Noire," by Dr. Sophie Pereyaslawzewa, ex-director of the 

 Sebastapol Biological Station. The title of the work does not, 

 however, exactly render' its contents, as the author has not only 

 given a monograph of forty-five species of Tutbellari;i; from the 

 Black Sea, of which twenty-nine species and the genus, 

 Darwinia, are new ; she deals also with the anatomy and 

 embryogeny of the Turbellaria;, and presents them in a 

 new light. The striking likeness between a young Accela and 

 an Infusorian— she says— must probably be considered as the 

 cause of the many errors committed as regards the Turbellaria; 

 altogether. Various authors have differed immensely in their 

 description of the Aca-la ; some have found in it no digestive 

 cavity, others have denied the histological differentiation of the 

 teguments ; others, again, have denied the existence of a nervous 

 system. It might have seemed that such instances would soon 

 have been dissipated when carefully-prepared sections were 

 resorted to ; but the sections, made by different explorers, 

 seemed to support the same views, as known from the works of 

 Graeff and Goethe.', Mrs. Pereyaslawzewa now maintains, and 

 supports her affirmations by carefully-prepared sections, that 

 the .\cct'la has a nervous system, -almost simultaneously dis- 

 covered by Metchnikoff, herself, and Delage, and demonstrates 

 that it possesses also a pharynx and a digestive cavity ; that its 

 teguments are histologically differentiated, and that the name 

 Acitla is not applicable to adult individuals, so that she has felt 

 bound to change this name into Pseudo-acoela. This very 

 elaborate monograph being published in French, it is accessible 

 to all men of science. It is illustrated with sixteen well-printed 

 plates, lithographed in Warsaw, from the author's own drawings. 



It is known that certain plant-stuffs (alkaloids, tannin, oxalic 

 acid, ic. ) protect plants from attack by animals. This function, 

 in the case of oxalic acid, has been recently studied by Herr 

 Giessler {Jenaischc Zeils.), taking species of rumex, oxalis, and 

 begonia. The acid mostly occurs in the epidermis and peri- 

 pheral tissues of the vegetative organs ; parts underground have 

 little or none. The leaves show most, but the acid may be 

 found in the stem, and the leaf and flower stalks. Curiously, it 

 dees not, like other protective matters, appear in young organs. 

 The older and more sappy the tissues, the more oxalic acid do 

 they contain. Snails, which avoided those plants in the natural 

 state, ate them when the oxalic acid had been precipitated. 

 The .substitution of various means of protection for one another 

 was elucidated by Stahl ; plants not protected mechanically have 

 chemical protection, and vice versa. In the plants studied by 

 Herr Giessler mechanical protection is deficient. Further, in 

 organs that have little or no oxalic acid, is found tannin. These 

 two " vicariate " with each other also in different species of a 

 genus. In many tissues both occur together. The protective 

 function of a secretion, lastly, does not exclude other functions. 

 Thus, regarding the epidermis as a water-reservoir, the osmoti- 

 cally very active organic acids doubtless play an important part 

 in the filling of the cells with water. The occurrence of begonia 

 and oxalis species in very dry places, as also the deficiency in 

 means of protection against transpiration, more pronounced the 

 higher the quantity of acid, put this function of oxalic acid in a 

 still clearer light. 



NO. I 23 I, VOL. 48] 



Prof. Sollas, F.R.S., communicated a paper on the 

 granophyre of the Carlingford and Morne mountains to 

 a recent meeting of the Royal Irish Academy. The grano- 

 phyre is everywhere intrusive into the gabbro, and owing 

 to the contrasted character of the two rocks it is possible 

 to trace out their relation in the fullest manner. The be- 

 haviour of the granophyre is of great interest ; from wide dykes, 

 comparatively few in number, it passes into innumerable thin 

 lamellar injections, which seam the gabbro through and through. 

 These can be further followed into cracks of microscopic 

 minuteness, and these swell out at intervals into ganglia, which 

 give a white spotted appearance to the otherwise almost black 

 gabbro. The ganglia are granophyric infillings of what were 

 once drusy cavities in the gabbro, and it is suggested that the 

 quartz so frequently found in gabbro associated with granitic 

 rocks, as e.g., at Carrock Fell, is of a similar origin. Of equal 

 interest is the abundance of gabbro fragments included in the 

 granophyre, and since the mineral constituents of the gabbro 

 present features peculiarly easy to recognise, there is no difficulty 

 in following the changes which they have suffered in con- 

 sequence of their immersion in the originally molten granophyre. 

 Thus the Bytownite, which frequently occurs as phenocrysts in 

 the granophyre, has frequently become surrounded by a mar- 

 ginal zone of orlhoclase, and the diallage can be traced into 

 amphibole and biotite and colourless granules of pyroxene, 

 which either remain in clusters about their place of birth or 

 are dispersed throughout the rock. It would, indeed, appear 

 that the ferro-magnesian con.stituents of the granophyre which 

 have led observers to designate it as syenite and augite grano- 

 phyre are entirely derived from the grabbro, and it hence 

 becomes an interesting question to consider whether in 

 numerous other instances rocks intermediate in composition to 

 the extremely acid and basic rocks with which they are assoc- 

 iated may not also have arisen from the admixture of two 

 already differentiated magmas, and not by the progressive 

 modification of a single original magma. 



At a recent exhibition by the French Societe de Physique, 

 MM. Mace de Lepinay and Perot showed a lecture-experiment 

 illustrating well the phenomenon of mirage. A long vessel with 

 plane sides contains a saline solution, on which is poured some 

 distilled water. By diffusion, the liquids gradually mix and 

 form a layer in which the density varies in a continuous way. 

 If now a ray be sent, by means of a reflector, slightly upwards 

 in the axis of the vessel, it describes a curve, passing through a 

 maximum and descending. Its trace on a vertical plate of 

 ground glass traversing the tube throughout its length, shows 

 exactly the path taken, and gives a very pretty effect. On the 

 same occasion, M. Pellin exhibited photographs of the fine 

 gratings produced by Prof Rowland, of Baltimore, whereby 

 fine lecture experiments in diffraction can be produced at but 

 small cost. 



An elegant method of optically studying the process of diffu- 

 sion in liquids is described by Herr O. Wiener in Wiedemann's 

 Annalen. It is somewhat similar to MM. de Lepinay and 

 Perot's beautiful imitation of the mirage, and consists in send- 

 ing a beam of parallel rays through a vessel containing 

 two liquids of different density and refractive power. A 

 trace of fluorescein makes the path of the rays visible, and 

 shows that they are bent away from the less highly refracting 

 liquid in the region where diffusion is taking place. By care- 

 fully pouring a layer of carbon bisulphide on to one of chloro- 

 form, and a layer of alcohol on the top of both, it is possible 

 to make the beam describe a wavy path, due to alternate re- 

 fractions by the alcohol and the chloroform, both of which are 

 less highly refractive than carbon bisulphide. For the purpose 

 of minutely investigating the process another arrangement is 

 adopted. Parallel rays of monochromatic light are sent through 



