484 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Liberation of Iron by Green Water-plants.* — IT. Molisch has si udied 

 the action of green water-plants towards compounds of iron dissolved in 

 water. Tin.' author finds that under the influence of light such plants 

 can bring about the dissociation of iron from its compounds. Many of 

 these plants give out an alkali, which, assisted by the oxygen liberated 

 during carbon-assimilation, favours the breaking down of such com- 

 pounds as iron acetate, iron citrate, etc. The liberation of iron from the 

 sulphate and malate appears to be retarded in some cases, but this may 

 be explained by the fact that some plants, e.g. Elodea, take up the iron 

 and store it beneath their epidermis, until no further iron remains out- 

 side the plant. Iron can be stored in the form of oxide both in light 

 and in darkness, but while the ordinary membrane of the epidermis is 

 unaffected by light, a second membrane is found in close connexion with 

 it on the upper surface, which is affected by light, and in this region the 

 iron is deposited in another form. 



The results obtained seem to show that submerged green water-plants 

 (such as Potamogeton, Ceratophyllum, Chora, Myriophyllum, Vallisneria, 

 Elodea, Riccia, and Ranunculus) and iron bacteria play an important 

 part in nature in removing iron from water and in furnishing material 

 for the formation of meadow iron-ore. 



Irritability. 



Action of Uitra-vioiet Rays upon Green Vanilla-pods. t — J. 

 Pougnet has experimented with green vanilla-pods, which are odourless 

 before they are ripe. Pods of varying degrees of greenness were exposed 

 to the action of ultra-violet rays, and the author was able to induce the 

 odour of vanilla in all cases, although in no case could he obtain crystals. 

 Pods thus treated retained their softness and almost their original size 

 for three months. Finally, they dried up, and in five months were only 

 one-fourth of their original volume. In a second series of experiments 

 the pods were treated with a O'OOl p.c. solution of MnCl 2 ; the effect of 

 the ultra-violet rays was thereby much accelerated and accentuated. 



Osmotic Pressure, and the Form and Structure of Plants.^ — J. 

 Beauverie publishes a final paper in connexion with his recent work upon 

 the alteration brought about in the form and structure of plants by 

 variation in the osmotic pressure of the surrounding media. The in- 

 vestigator's first experiments were made with the lower fungi, e.g. Asper- 

 gillus, Penicillium, etc. ; increased osmotic pressure in the culture- 

 solution brought about a decrease in height of the aerial parts of the 

 plant, together with lateral expansion of the cells, while the submerged 

 portions became relatively of more importance. The experiments were 

 then extended to Phaseolus, Pisum, Lupinus, Zea, and other higher 

 plants. Seeds were grown in pure water, and in most cases hydrotropism 

 was most marked, being more powerful than geotropism in the effect 

 produced upon the roots. Seeds were then grown in a solution of 

 common salt, with other conditions as before. The strength of the solu- 

 tion was increased each day until a concentration of 1'5 p.c. was reached. 



* SB. Akad. Wiss., cxix. (1910) pp. 959-84 (1 pi.). 



+ Coniptes Rendus, clii. (1911) pp. 1184-6. 



\ Rev. Gen. Bot., xxiii. (1911) pp. 212-19 (8 figs.). 



