JlT.Y, 19i; 



KNOWLEDGE 



271 



BIOLOGY OF SALT-MARSH PLANTS. — Two 

 interesting papers have recently appeared which deal with 

 the physiology of certain halophytic plants growing in salt 

 marshes. Miss Delf (Ann. Bot.,W\'), describes experiments 

 in which the loss of water by transpiration is estimated by 

 measuring the total transpiring surface and observing loss of 

 weight during withering. The author concludes that typical 

 halophytes like Salicornia and Siiacda have a high rate of 

 transpiration which is comparable with, or may be even 

 greater than, that of a typical mesophyte like the broad bean. 

 Statistics are given of the distribution and number of stoinata 

 per square centimetre in various salt-marsh plauts. The 

 stomata of Salicornia and Aster fripoliiim are not sunken 

 nor protected by cuticle to any great extent, but rather 

 resemble those of a typical mesophyte in being superficially 

 placed, cap.able of opening and closing, and sensitive to light 

 and to changes in humidity of the air. The stomata of Sali- 

 cornia seem to lose power of movement after the flowering 

 period, and then remain permanently closed ; those of Aster 

 tripolium were seen to open in air nearlj- saturated with 

 water vapour, but closed in air with seventy-five per cent, 

 humidity; those of Stiaeda and Afriplex were never seen 

 open at all. 



Miss Halket iXew Phytologist. XI describes experiments 

 made with the object of ascertaining whether or not salt- 

 marsh plants with high osmotic pressures can obtain water 

 from atmospheric moisture and from sea-water. It was found 

 that these plants can absorb water even when immersed in 

 salt solution, whereas non-halophytic plants like the primrose 

 decrease in weight when immersed in salt solution, though 

 tliey increase when immersed in distilled water. The root- 

 system of these salt-marsh plants is small in proportion to 

 their size, hence the amount of water absorbed by the root is 

 probably relative!}- small ; the water obtained from atmospheric 

 moisture through absorption by the aerial parts may compensate 

 the plant for this smallness of root absorption. 



BIOLOGY OF SELAGINELLA.— In a previous note 

 in these columns ("Knowledge,"' 1911, page 350), some of 

 the results of recent work on the reproduction of Sclaginella 

 was summarised. Seyd iliiaug.-Diss.. University of Jena) 

 has published an interesting account of his observations on 

 the biology of the vegetative organs of this well-known type. 

 He has made experiments on the taking-up of water by the 

 leaves, which had already been noted by previous writers but 

 not fully investigated by them. He beheves the ligule of the 

 leaf is largely concerned in this absorption of water, and has 

 made some ingenious and interesting experiments on this 

 point. He placed shoots of Sclaginella in solutions of 

 various chemical substances and dyes, and the results in 

 every case showed that the absorption occurred at the ligules 

 of the leaves, and diffuses thence into the vascular bundles. 

 Previous writers had suggested that the chief or sole function 

 of the characteristic ligule of this genus is to protect the 

 growing-point of the shoot and the young leaves. Seyd also 

 experimented with the rhizophore and found that this organ 

 absorbs water and salts only when it has reached the soil and 

 produced root-hairs. 



NAKED-EYE AN.A.TOMY OF PLANTS.— Teachers and 

 students of Botany are so accustomed to rely upon the com- 

 pound microscope that they probably do not realise what a 

 large amount of plant structure can be made out with the 

 unaided eye or with a low-power pocket-lens. A useful and 

 interesting paper by .-Vroichovskij iBiill. jard. imp. bot. St. 

 Petersboiirg, XII. 1) — unfortunately in Russian, but with a 

 summar>' in German — contains an account of various materials, 

 some well-known and others new, suitable for this purpose. 

 The stems of cucumber and vegetable marrow, as is known 

 to most teachers, have unusually large and distinct vessels in 

 the wood, as well as large cells, and form an unrivalled intro- 

 duction to the microscopic study of the tissues of plants. 

 Almost equally suitable are the stems of balsam and begonia, 

 while large cells (sometimes over a millimetre long! are to be 

 seen in the flesh of the arbutus fruit, the epidermis of unripe 

 tomatoes, and the epidermis of the leaves in various plants — 

 e.g., Tradescantia, begonia seedlings. Very large cells also 



occur in the leaves of various succulent plants, such as 

 Echcveria, Meseinbryanthcmiiin, Klcinia, Crassiila. Aloe. 

 The nucleus can be plainly seen with a lens magnifying ten 

 diameters, in the fiesh of the arbutus fruit, and the streaming 

 of the protoplasm in the enormously elongated cells of the 

 stonewort Nitella is equally easy to see with a low-power 

 lens or even with the unaided eye. The same simple method 

 suffices for making out the distribution of the stomata in the 

 leaves of the spruce fir and of various succulents — Agave, 

 Klcinia, many cacti, and so on. 



CHEMISTRY. 



By C. AiNswoRTH Mitchell, B.A. (Oxon.), F.I.C. 



DEVITRIFIC.\TION OF SILICA GLASS.— Sir William 

 Crookes describes in The Proceedings of the Royal Society 

 (1912, LXXXVI, A, 406) a curious experiment upon a tube of 

 silica glass. When this was exhausted and heated for se%eral 

 hours at a temperature of 1300° C. its structure was completely 

 altered, and it had become devitrified to such a degree 

 that it had become permeated to the extent of about eight 

 per cent, with air. On repeating the exhaustion and heating 

 the infiltration of air was found to have attained 46-6 per cent, 

 of the capacity of the material, while in the case of a similar 

 tube of ordinary glass only a minute bubble of air had 

 entered. 



Examined under the microscope the devitrified silica showed 

 that the surface was broken up into cells, some of which w^ere 

 hexagonal. The effect closelv resembled that produced by 

 evaporating a solution of radium bromide in a silica dish, 

 though when no heat is applied radium salts can be kept for 

 many years in either silica or glass vessels. The devitrifica- 

 tion of silica is thus caused either by exposure to a very high 

 temperature or by the action of salts of radium at the tempera- 

 ture of boiling water. 



ALCOHOL AND YEAST FROM BANANA MEAL.— 

 A cheap process of manufacturing alcohol is described by 

 Herr C. Nagel (Zeit. Spiritiisind., 1912, XXXV, 185), 

 banana meal being used as the original material. The fruit, 

 which must be unripe, since otherwise it forms a sticky mass 

 when dry, is peeled, dried and ground to a meal. The meal 

 is mixed with water and a little malt extract, and mashed at a 

 temperature of 140° to 160° F. so as to effect the saccharifica- 

 tion of the starch. This is brought about by the action of a 

 diastase which is present in the banana, and to which the 

 change of starch into sugar during the ripening of the fruit 

 is due. 



After completion of the mashing process the wash is cooled 

 and set with a suitable yeast, which ferments the sugar into 

 alcohol, a yield of 42 to 47-8 litres being obtained from 

 one hundred kilogrammes of the meal, the cost of which is 

 about sixty shillings. 



The addition of the malt extract to the mash was found 

 necessary for obtaining a good yield of alcohol, the c]uantities 

 being much lower when the malt was omitted. 



.\ wash obtained from a mixture of banana meal and malt, 

 in the proportions of two to one, is an excellent medium for 

 the cultivation of yeast of excellent quality, the yield 

 amounting to about a fifth of the weight of the original 

 materials. 



ALLOYS OF RADIUM.— Messrs. de Mare and Jacobs 

 describe the production and properties of an alloy of radium 

 and silver in a communication to a Belgian journal, which is 

 abstracted in the Cheni. Zentralbl. (1912, I, 1430). The 

 new alloy, which was obtained by reducing a mixture of silver 

 chloride and radium sulphate by means of calcium carbonate 

 and charcoal in a gas furnace, was a yellowish radio-active 

 substance, which was sufficiently tenacious to be drawn out 

 into a thin wire. 



A deposit, possibly of the nature of an alloy, was also 

 found to be formed upon the cathode, when a solution of 

 radium acetate was electrolysed with platinum electrodes. 

 The deposit was a brown substance, which was very radio- 

 active. 



