February 25, 1916] 



SCIENCE 



289 



toiacter, he says: "On standard media, it 

 grows only moderately, but, on the contrary, very 

 well on gypsum plates which have been wetted 

 with mannite solution." The writer in making a 

 quantitative survey of the bacteria in various 

 groups of soil organisms, found it necessary to 

 modify and invent new media for the Azotoiac- 

 ters and nitrifying organisms; after considerable 

 experimental work it was found that the ingredi- 

 ents of a good radicicola or Aeotoiacter medium 

 in a soil extract agar, to which, after tubing was 

 added, about .5 gram of a mixture of insoluble 

 salts, including the carbonates of calcium and mag- 

 nesium, with kaolin, would bring out the nitrogen- 

 fixing organisms (Azototacters, B. radioieola, B. 

 radiobcwter) and the nitrifying organisms {Nitro- 

 somonas and Nitrobacter) . Some of the stand- 

 ard media worked fairly well when balanced by the 

 insoluble minerals. By use of qualitative chem- 

 icals the active nitrifying colonies could be easily 

 demonstrated on the plate. These media differ 

 from others in that the insoluble minerals in the 

 tube are shaken up at the time of inoculating and 

 poured into the Petri dish. The studies again 

 emphasize the importance of basic compounds, 

 humus and symbiosis in bringing out Aeotobacter. 

 The western soils (Colorado, North Dakota) show 

 many Azotobaeter chrooooccum. 



Feat Organisms that Slowly Liquefy Agar (illus- 

 trated by culture) : Thomas F. Manns. 

 While making a study of the flora of raw peat 

 and muck, the writer observed that certain col- 

 onies of bacteria were able to completely break 

 down the agar and cause deep pitting in the me- 

 dium. The writer has never met with similar or- 

 ganisms in his extensive culture work on agricul- 

 tural soils. They are probably quite closely eon- 

 fined to peat and moor soils. Erwin P. Smith 

 mentions in Volume I., "Bacteria in Relation to 

 Plant Disease," p. 32, that "Metcalf has de- 

 scribed a bacillus which slowly softens it (agar), 

 and the writer has observed similar phenomena." 

 The organism, which appears to be a micrococcus 

 of about one micron in diameter, was found most 

 abundant in peat that was composted with floats 

 {ground calcium phosphate) and calcium carbon- 

 ate, 200 lbs. of each to a ton of the former. The 

 writer has made no extensive morphological, physio- 

 logical or cultural studies upon the organisms. 

 Note of its occurrence is made here solely from 

 the interest that enzymes of such active properties 

 are produced by bacteria. This agar-digesting or- 

 ganism was grown on the following medium: 



Grama 

 Mono-potassium-phosphate (K H. PO,) . . . 4.00 



Wood ashes (chestnut) 12.00 



Ferric sulphate .25 



Mannite 10.00 



Agar 12.00 



Water 1,000.00 



Some Observations on the Occurrence of Sterile 



Spilcelets in Wheat: A. E. Grantham. 



The examination of a large number of varieties 

 of wheat grown at the Delaware Agricultural Ex- 

 periment Station during 1915 indicates that there 

 is considerable variation in the percentage of ster- 

 ile spikelets per spike among the leading varieties 

 of winter wheat. The study included observations 

 on wheat sown under ordinary field conditions and 

 by the centgener method. It was noted that the 

 varieties grown under field conditions exhibited a 

 higher percentage of sterile spikelets than where 

 the plants were grown 6 inches apart each way as 

 under the centgener method of planting. That is, 

 the thickness of planting appeared to be a factor 

 directly related to the frequency of sterile spike- 

 lets. The number of sterile spikelets per spike 

 (the average of 25 spikes for each variety) and 

 the percentage to the whole number of spikelets 

 were determined for 188 varieties of wheat. Of 

 these varieties SO were beardless and 108 were 

 bearded. The average percentage of sterile spike- 

 lets in the bearded varieties was found to be 25.1 

 per cent., while the beardless averaged 17.8 per 

 cent. This indicates that the bearded varieties, as 

 a class, have a higher percentage of sterile spike- 

 lets than the beardless wheats. Only 20 of the 80 

 varieties of beardless wheats had more than 15 per 

 cent, of sterile spikelets, while not a single variety 

 of bearded wheat had less than 17 per cent, sterile 

 spikelets. Forty-five of the 108 bearded varieties 

 had 25 per cent., or more, sterile spikelets. Of the 

 80 beardless varieties only 2 had 25 per cent, ster- 

 ile spikelets. The occurrence of sterile spikelets 

 was also noted on two varieties of wheat (one 

 bearded and the other beardless), when planted at 

 different dates. The two varieties were planted at 

 seven-day intervals from September 17 to October 

 22, on fertilized and unfertilized soil. The wheat 

 planted at the earlier dates, whether fertilized or 

 not, had a higher percentage of sterile spikelets 

 than the later seeding. In this case, also, the 

 bearded variety had the higher per cent, of sterile 

 spikelets. Two varieties of wheat fertilized with 

 different combinations and quantities of plant food 

 exhibited considerable variation in the number of 

 sterile spikelets. Phosphoric acid and potash used 



