Apkil 7, 1911] 



SCIENCE 



543 



Comparison of numbers of bacteria in mud 

 deposits on the harbor bottom in samples collected 

 from polluted and unpolluted sections. 



Eolation of channels and shoals to bottom de- 

 posits and bearing of this upon the oyster in- 

 dustry. 

 Biochemical Factors in Soil: M. X. Sullivan. 



The soil is not an inert reservoir for plant food, 

 but is the seat of physical, chemical and vital 

 actions, the biochemical factors being especially 

 prominent. Numerous bodies which occur in soOs 

 and arise either in the metabolic activities of 

 microorganisms or are left in the soil after the 

 decomposition of the plant and animal debris and 

 perhaps occur also as a result of excretion from 

 roots or from cell sloughing, play a considerable 

 role in soil fertility. Some of these substances 

 are harmful to plants, some beneficial. Fertilizers 

 do work in soil in modifying the physiological 

 functions of the microorganisms by bringing about 

 suitable conditions for their development, in stim- 

 ulating or retarding their digestion of inert bodies, 

 and in furthering their enzymotic functions. Soils 

 per se have oxidizing and catalyziug properties, 

 while poor soils have these functions in a much 

 lessened degree. Oxidation in subsoils which are 

 of much poorer productivity than the surface soil 

 is usually very slight. 

 Bacteria of Frosen Soil: H. J. Conn. 



Results of work at Ithaca, N". Y., during 1909- 

 10, showing a phenomenal increase in soil bacteria 

 during the winter. Quantitative results already 

 published.^ Qualitative work includes the study of 

 about 300 cultures. 



Quantitative Results. — Increase from 7 millions 

 per gram in November, 1909, to 33 millions in 

 February, 1910, and from 8 in November, 1910, 

 to 22 in December, 1910. These results are new, 

 but are not disproved by previous work. 



Possible Explanation. — There seem to be two 

 different groups of organisms, one increasing in 

 warm, the other in cold weather; the former re- 

 quires so much organic food that a rapid increase 

 is impossible. 

 Evidence in Support of this Explanation — 



Belation to Moisture Content. — Germ content 

 and moisture content are usually parallel; the 

 exceptions to this rule are such as to suggest an 

 alternation in predominating types. 



Relative Numbers of Rapid Liquefiers, Actino- 

 m,ycetes and Sloiv Growers. — The last group in- 

 creases in winter. 



= CentU. f. Baht., II. Ab., 28, pp. 422-434. 



ve Results. — There are certain organ- 

 isms present throughout the year. The others 

 appear only at times and show a tendency to reap- 

 pear at the same season another year. Fall and 

 winter show the greatest diversity of types. 



Classification of the types studied in this work: 



1. Higher filamentous bacteria. Actinomyces. 



2. Rapid liquefiers, producing spores. Mostly of 

 the B. subtilis group. 



3. Rapid liquefiers, without spores. All but one 

 Pseudomonas forms. 



4. Slow growers — without spores, producing 

 punctiform colonies; partly show liquefiers, partly 

 non-liquefiers. 



Medium used in quantitative work: Gelatin, 12 

 per cent.; dextrose, 0.1 per cent.; soil extract, 20 

 per cent. Reaction adjusted with NaOH to 0.5 

 per cent, acid to phenolphthalein. Soil extract for 

 this medium prepared by boiling 30 minutes with 

 an equal weight of w&,ter, then filtering. 



Incubation period in quantitative work: 7 days. 

 Temperature of incubation: 19°. 



Viability of P. radicicola on Ash-maltose-agar : 



5. F. Edwabds. 



During the summer and autumn of 1906, cul- 

 tures of P. radicicola were isolated from the nod- 

 ules of nineteen hosts, an ash-maltose-agar. Col- 

 onies were transferred to the same mediiun in 

 Freudenreich flasks which were kept in a darkened 

 cupboard at laboratory-room temperature. Dur- 

 ing the autumn of 1910, plates were made from 

 these old cultures with the result that in fifteen 

 of them the organism was still living. The results 

 are shown in the following table: 



In every ease in which growth occurred, the 

 colonies were typical, and stained preparations 

 and hanging drops showed the typical characters 

 of P. radicicola. 



Pot tests in sterile sand were started, using 

 seeds of alfalfa, red clover, peas and beans. At 

 the time of writing, only the peas were sufficiently 

 developed to examine. Of six: control plants, not 

 inoculated, three showed no nodules, and three 

 showed 1, 10 and 12 nodules, respectively. Six 

 plants inoculated with the 1906 culture showed 18, 

 33, 20, 25, 64 and 25 nodules, respectively. Stains 

 from the nodules showed rod and branched forms 

 typical of P. radicicola, and plates showed abun- 

 dant growth in five days on ash-maltose-agar at 

 room temperature. The work thus far shows evi- 

 dence that P. radicicola retains its virility as well 

 as its vitality after considerable periods of time 

 in stock cultures under laboratory conditions. 



