August. 1913. 



KNOWLEDGE. 



307 



and after germination they are found occupying the growing 

 tip of the young shoot, so that the relationship between the 

 bacteria and the higher plant is extremely intimate and begins 

 at a very early stage. The author killed the bacteria with 

 hot water without injuring the embryo, and found that the 

 young plants thus sterilised, or freed from bacteria, grew very 

 slowly and had small leaves as compared with normal or 

 infected plants. Sand cultures of sterilised and unsterilised 

 seedlings showed that the former died in the absence of a 

 supply of nitrogenous food materials, while the latter grew 

 quite well. Precautions were taken in these cultures to 

 exclude other micro-organisms. 



CYTOLOGY OF BACTERIA.— In a long paper on the 

 cytology of bacteria, Dobell (Q.J.M.S., Vol. LVI) prefaces his 

 own observations by a useful and interesting summary of 

 previous work on the structure of bacteria, with special 

 reference to the methods of fixation and staining used by the 

 various investigators and to their conclusions concerning the 

 presence or absence of a nucleus in these organisms. He 

 examined a large number of forms, obtained from the 

 intestines of various animals, and arrived at the following 

 conclusions. All bacteria which have been adequately 

 investigated have a nucleus; but the form of the nucleus is 

 variable, not only in different bacteria, but also at different 

 periods in the life-cycle of the same species. The nucleus 

 may be in the form of a loose system of granules (chromidial 

 nucleus) ; or of a filament of variable configuration ; or of 

 one or more relatively large aggregated masses of nuclear 

 substance ; or of a system of irregularly branched or bent 

 short strands, rods, or networks ; and probably also in the 

 vesicular form characteristic of many plants, animals, and 

 protista. There is no evidence that non-nucleate bacteria 

 exist. The author considers it highly probable that the 

 bacteria are in no way a group of simple organisms, but 

 rather a group displaying a high degree of morphological 

 differentiation, coupled in many cases with a life-cycle of 

 considerable complexity. 



BIOLOGY OF THE PITCHER-PLANT DISCHIDIA. 

 — In the genus Dischidia belonging to the Asclepiadaceae 

 and found in the East Indies as epiphytes climbing by 

 adventitious roots and having fleshy wax-clad leaves, some 

 species have, in addition to ordinary leaves, remarkable 

 pitcher-leaves. Each of these is a pitcher with an incurved 

 margin and about four inches deep ; but their biology is very 

 different from that of such pitcher-plants as Nepenthes. 

 Into the pitcher there grows a root which arises from the 

 stem or from the leaf-stalk close to the pitcher, and this root 

 ramifies among the humus and other debris which is apparently 

 largely carried into the pitcher by ants. The pitcher also 

 catches rain-water, hence it serves as a humus collector and 

 water reservoir ; the inner surface is coated with wax, hence 

 the water cannot be absorbed by the pitcher itself, nor lost 

 by passing through the walls, but must be absorbed by the 

 roots; the inner surface of the pitcher also bears stornata, and 

 doubtless the water-vapour given out through these is con- 

 densed in the pitcher. 



Some further details of the biology of Dischidia have 

 recently been given by Kerr (Proc. Roy. Dublin Soc, Vol. 

 XIII) from observations made on the pitcher-bearing species 

 D. Rafflesiana and on D. nutntnularia in their native 

 habitat in the jungles of Northern Siani. The plants are 

 associated with two species of ant (Iridomyrmex 

 myrttiecodiae, I. cordex). In D. nutntnularia the ants are 

 found below the leaves, where they form nests of clay and 

 vegetable debris in which the roots of the Dischidia branch ; 

 while in D. Rafflesiana the ants make their nests within the 

 pitchers and plaster clay above the bases of the pitchers and 

 over the roots. The flowers are pollinated by bees, but the 

 ants assist in the dispersal of the seeds, removing them for 

 food — the seeds not eaten germinate along the ants' tracks. 

 The author concludes that in D. Rafflesiana the pitchers do 

 not so much store water as serve to economise the water 

 vapour of transpiration and also provide shelters for ants, 

 which in return supply the roots with food material. 



CHEMISTRY. 



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



ARGON AND ITS PLACE IN NATURE.— An outline of 

 a communication on this subject made by Sir William 

 Ramsay, to the Chemical Society of Rome, is given in the 

 Chemical Trade Journal (1913, LII, 595). The experiments 

 of Professor Collie and Mr. Paterson, which indicated the 

 formation of helium and neon from hydrogen, have been 

 repeated and their results confirmed. In the opinion of Sir 

 William Ramsay dry hydrogen becomes polymerised into 

 helium, when subjected to the action of cathode rays in a 

 vacuum tube, while for the production of neon the presence of 

 oxygen is necessary. This might be derived either from a 

 trace of moisture or from the bombardment of the glass by the 

 rays. When the experiment was modified by placing dry 

 hydrogen in a vacuum tube and passing an electric discharge 

 for five or six hours between an aluminium cathode and 

 anode, which were coated with sulphur, argon was produced, 

 but no trace of helium or neon could be detected. Again, 

 when the electrodes were coated with selenium instead of 

 sulphur the gas, after the experiment, showed the character- 

 istic lines of the krypton spectrum. The three elements 

 neon, argon, and krypton, the atomic weights of which are in 

 an ascending scale, have thus apparently been produced from 

 hydrogen in the presence of oxygen, sulphur, and selenium 

 respectively — elements which stand in an analogous relation- 

 ship towards each other. 



BIOLOGICAL METHOD OF IDENTIFYING SEEDS.— 

 The precipitin method of distinguishing between the flesh 

 and blood of different species of animals was described some 

 years ago in these columns. In brief, it is based upon the 

 fact that when the serum of a particular animal is injected 

 into, say, a rabbit, the serum of the latter becomes 

 immunised, and when subsequently the rabbit is killed its 

 serum will give a precipitate with the serum of animals of the 

 species to which it was rendered immune, but not with the 

 serum of an animal of another species. 



This method has now been successfully applied to the 

 identification of the seeds of different plants, and an account 

 of the process devised by Relander is given by Dr. Zade in 

 ' the Bull. Agric. Intel, and of Plant Diseases (1913, IV, 200). 



The seeds — wheat, for example — are finely powdered and 

 extracted with physiological salt solution. The filtered extract 

 is then injected, in small quantities at intervals of three to ten 

 days, into a small animal. After a suitable period the blood 

 serum of this animal is separated and filtered, and the filtrate 

 tested with a few drops of an extract of the seeds under 

 examination. If these are of the same kind as the original 

 seed a precipitate will be produced, whereas the liquid will 

 remain clear on the addition of extracts from other kinds of 

 seeds. 



By this method Relander obtained a precipitate on 

 adding extracts of two-rowed barley to the serum of a rabbit 

 which had been treated with a similar extract, whereas no 

 precipitate was obtained with extracts of six-rowed barley. 

 In the same way it was found possible to distinguish between 

 American, Italian, and Norwegian clover seeds, but Finnish 

 seed reacted in the same manner as Norwegian seed. 



By means of this test it should be practicable to distinguish, 

 prior to cultivation, between awned and awnless varieties of 

 wheat, which has hitherto been impossible. 



CARBON TETRA-IODI DE.— An iodide of carbon, 

 CL, which crystallises in ruby-red octahedra, having a 

 specific gravity of 4-50 at 0° C. was first obtained in 1885 by 

 the action of iodides upon organic chlorine compounds. The 

 various reactions by which the tetra-iodide may be prepared 

 have recently been studied by M. Lantenois (Comptes Rendus, 

 1913, CLVI, 1385). In order to avoid decomposition of the 

 product it is necessary not to let the temperature exceed 

 92° C, and the most satisfactory results have been obtained 

 by heating lithium chloride for five days at that temperature 

 with an excess of carbon tetrachloride in a sealed tube. A 

 pure product could also be prepared by treating iodoform 

 with a hypochlorite. 



