Fib. 



^0 



NA TURE 



311 



tures up to 60° C, is described and figured at p. 348, and 

 consists essentially of a closed vessel with triple walls, 

 the space between the inner and middle plate filled with 

 water, the outer containing air. For higher temperatures 

 a simple tin plate thermostat was employed, the space 

 being filled with water for temperatures up to 100° Cent, 

 and with glycerine or oil for higher temperatures. The 

 source of heat was always a gas-flame with the usual 

 thermo-regulator. Numerous tabulated results are given 

 of experiments upon moist and dry seeds at various tempe- 

 ratures, and it was found, as might be anticipated, that 

 perfectly dry seeds can withstand a high temperature, 

 even between 120° and 125° Cent, without injury. 



Dr. Koch describes how bacteria can be observed, pre- 

 pared, and photographed, this paper forming the sixth of 

 the extremely important series of researches on bacteria 

 which have from time to time appeared in the Beitrdge. 

 A thin layer of bacteria with the fluid containing them is 

 to be dried on a thin cover of glass. By placing the glass 

 cover with the dried material in absolute alcohol, or better, 

 in a o'5 per cent, solution of chromic acid, the bacteria 

 are fixed to the cover, although the coagulated ground 

 substance in which the bacteria are imbedded can be 

 made to swell up and the bacteria themselves to resume 

 their natural forms when the cover is placed in a solution 

 of acetate of potash (i part to 2 of distilled w-ater). The 

 bacteria can be coloured by means of aniline, the best of 

 all being aniline brown ; but methyl violet and fuchsia 

 will also answer. The stained object can be preserved 

 permanently on slides by mounting in Canada balsam, 

 concentrated solution of acetate of potash, or in glycerine. 

 Twenty-four photographs of bacteria, mostly from speci- 

 mens stained with anihne brown, illustrate the paper ; 

 and in some, as 5 and 6 on Plate XIV., the cilia of 

 bacillus are very beautifully shown, magnified 500 and 

 700 diameters. Koch finds that it is easier to photo- 

 graph the cilia than to observe them directly with the 

 microscope. 



The other papers in this part are on certain Usti- 

 laginae, by Dr. Schroeter ; and on two new species of 

 Entoroophthora (J£. conglomcrata and E. riinosd) dis- 

 covered upon dead gnats, by Prof. N. Sorokin. 



The first and second parts of vol. iii. contain eleven 

 papers. Four of these are devoted to Bacteria, and form 

 the seventh to the tenth of the series of Researches on 

 Bacteria already alluded to. The titles of the papers are 

 VII. Experiments on Infection with Micrococcus pro- 

 digiosiis, by Dr. A. Wernich ; VIII. Researches on the 

 Bacteria in Air, by Dr. Miflet ; IX. On the Action of the 

 Electrical Current on the Multiplication of Bacteria, by 

 Dr. F. Cohn and Dr. Mendelssohn ; and X. Studies of 

 Blue Milk, by Dr. F. Neelsen. Two of these papers 

 may be briefly mentioned. By means of a specially con- 

 trived apparatus fitted with a new continuous aspirator 

 the invention of Paul Boehme in Brunn, atmospheric air 

 from different localities was examined. These were (i) 

 air in Botanical Laboratory; (2) in Fever Hospital ; (3) 

 in the Pathological Theatre ; (4) in the Surgical Theatre; 

 (5) air in Botanic Garden ; (6) air for soil ; and (7) air for 

 drains. The results were briefly as follows: — i. Germs 

 of bacteria capable of developing are abundant in the air, 

 and could readily be collected and cultivated in a special 

 mineral solution, malt extract, or [solution of Liebig's 



extract of beef. 2. Many forms of bacteria can produce 

 reproductive germs in air, while others, as B. Tenin', seem 

 only capable of producing germs in putrescent matter. 

 3. Air from the soil contained occasionally germs of 

 bacteria. 4. .Air from the Fever Hospital contained no 

 germs, owing to the completeness of the ventilation and 

 disinfection. 5. Air from a sewer contained abundance 

 of germs of bacteria capable of reproducing. 



Neelsen, in his paper on Blue Milk, finds that the 

 special organism in it may assume three or four different 

 forms, sometimes like Bacterium, then like Bacillus, then 

 hke a Chroococcus, and lastly like a Leptothri.^c. He 

 discusses the Theory of Cohn and others that the Bacteria 

 form many separate genera and species, and the Theory 

 of Lankester and Warming, that they are forms of a 

 protean species, and seems to conclude that the germs of 

 a given form may under different conditions develop in 

 one or other direction, as observed by him in blue milk. 



Dr. Schroeter continues his observations on the Deve- 

 lopment of Ruit, and Dr. Oscar Kirchner describes the 

 Development of Voh'o.i minor, Stein. Dr. Hielsher 

 describes the Anatomy and Biology of the Genus Strep- 

 tocarpus, and details many interesting facts regarding 

 that curious and beautiful genus. When the seed of 

 Streptocctrpus polyanthus germinates, numerous adven- 

 titious roots form on the primary axis, one of the two 

 cotyledons soon disappears, while the other develops 

 greatly, and forms a perennial foliage leaf. On the 

 petiole of this leaf numerous adventitious roots develop 

 and the primary axis disappears. The leaf produces 

 adventitious buds from which the flowers develop, while 

 it also develops a series of adventitious leaf-buds. Dr. 

 Beinling contributes a paper on the formation of adven- 

 titious roots and buds on the leaf-cuttings of Peperomia. 

 Prof. Klein describes in detail the anatomy oi Pinguicula 

 alpina as an insectivorous plant, and points out that the 

 plant occurs in two forms, one with green leaves, the 

 other with the leaves more or less red-brown in colour, 

 and that the tissues assume an intense yellow colour 

 when acted on svith caustic potash solution. The re- 

 maining papers are by Dr. Schwartz, Chemico-botanical 

 Studies on the Acids in Lichens, and Dr. Eidam on the 

 Gymnoasci. The various papers ably sustain the repu- 

 tation of this work, and all of them will well repay 

 careful study. 



LETTERS TO THE EDITOR 



[The Editor does not hold himself responsible for opinions expressed 

 by his comspondtnts. Neither can he undertake to return, or 

 to correspond ivith the writers of, rejected manuscripts, N' 

 notice is taken of anonymous communications. 

 The Editor urgently requests correspondents to keep their letters as 

 short as possible. The pressure on his space is so great that it 

 is impossible otherwise to ensure the appearance even of com- 

 munications containing interesting and novel facts. ^ 



Dust and Fogs 



I MUCH regret the Hon. R. Russell, in his letter to Nature, 

 vcl. xxiii. p. 267, takes such an extremely desponding view of 

 the influence whicli my experiments on cloudy eondensalion arc 

 likely to exercise upon the present attempts to rid the atmofphere 

 of our large towns of their ever-recurring fogs. The object of 

 these experiment"; was to find out what caused fogs, in the hope 

 that with the knowledge thus acquired we might be better able 

 to find a remedy. The preferable course seemed to be to find 

 the cause first, and then if possible devise some remedy, rather 

 than try remedies at haphazard. 



