Vol. XVI. Xo. 394. 



THE AGRICULTURAL NEWh 



171 



are still attached to the trees. T. (fijf'ardi, on the other 

 hand, parasitizes larvae in fallen fruit to a much greater 

 e.vtent than any of the othens, and it is thought that this para- 

 .site will prove most useful in supplementiuK the work of the 

 other three speeies of larval-parasites. The data published by 

 Back and Peniberton show that all four parasites have 

 successfully established theniselveM and already promise to be 

 an iiuportunt factor in the control of Ceratitis capilata in 

 Hawaii. These parasites have so far found conditions 

 unusually favourable, with an abundance of hosts and 

 apparently no uatural enemies, and it remains to be seen 

 how they will survive in the struggle for existence which will 

 come later. 



THE DOMINICA GREEN LIME TRADE 



With the object of improving the conditions pertaining 

 to the transportation of green limes from Dominica, certain 

 recommendations made by the principal shipfiers have been 

 published in the Dotidniia Chronicle (April 28, 1917). 

 The recommendations were formally submitted by the 

 Chamber of Commerce to the Government, and the idea is 

 that every shipper shall be made to conform to these sug- 

 gestions. The Chamber of Commerce states first of all that 

 they are not satisfied with the conditions prevailing at 

 present in the green lime industry. In the interest of the 

 trade the best means of preventing the exportation of bad, 

 immature, and ripe fruit, would be to .'uggest to all shippers 

 that a packing card with the name of the shipper, steamer, 

 packer, and wrapper, also date of shipment be inserted in 

 each package, with space for the receiver to insert date of 

 inspection in Xew \uTk. It is suggested that any com 

 plaints should be reported to the Chamber of Commerce who 

 would make investigations on receipt of such complaints. 



It is regarded as being very important that the limes 

 should be graded. In regard to the picking of the fruit, it is 

 sujigested that clippero should be used, in.stead of the fruit 

 being torn from the trees. 



Shippers should avoid leaving the packed limts in the 

 sun or rain, not should they cover the packages with tar- 

 paulins several days before the limes are shipped. The fruit 

 should be stored in a cool and dry place pending the arrival of 

 the stfamer.and all limes should be allowed to cure for at least 

 forty-eight hours before they are wrapped and packed. The 

 question of using a trade mark is raised by the Chamber of 

 Commerce; also the possibility of irrigating certain fields 

 with a view of forcing the fruit at a time when the demand 

 is greatest. It is recommended that in order that the fruit 

 may have a bright clean skin, potassic* manure should be 

 used when obtainable. 



Lastly, in view of the fact that the packages of green 

 limes often arrive in New York in bad order, longer nails 

 should be used for the coopering of the barrels. ''-,JI 



A reference to the future of the Dominica green lime 

 trade with New York will be found in the A<jricH' final 

 News for March 10, 1917, p. 7-". 



The St. Vincent Government Cotton Ginnery is now 

 offering for sale at 5c. per lb., selected and disinfected Sea 

 Island cotton seed of excellent germination. The cotton from 

 which the seed has been obtained has been specially bred from 

 a single plant by the Agricultural Department. It is of good 

 ordinary grade, very even and fine. ' 



SOIL PROTOZOA AND SOIL 

 STERILIZATION. 



An exhausitive review of investigation in soil protozoa 

 and soil sterilization, by N. Kopeloff and D. A. Coleman 

 appears in Soil Science, (Vol. Ill, Xo. 3). It is held that 

 Itussell and Hutchinson's contention that sterilization 

 eliminates a biological factor (protozoa, which are supposed 

 to feed upon beneficial soil bacteria), has not been accepted 

 by the majority of investigators working along the same 

 lines. Reference is also made to Koch's theory of direct 

 stimulation, Hiltner and Stormers theory of indirect stimu- 

 lation, Pickering and Schriner's chemical explanation of the 

 problem and Greig-Smiths bacterial toxin hypothesis, all of 

 which require, in the opinioh of the revieweis, more investi- 

 gation before any one of them can be accepted in au unquali- 

 fied manner. 



It is believed by the reviewers that the scope of unsolved 

 problems in connexion with the subject is considerably 

 broader than the investigations already carried to completion. 

 How to sterlize the soil without altering its chemical 

 composition is an important though baffling problem. On 

 the bacteriological side, it is submitted, much can and needs 

 to be done in determining the differences in the physiological 

 efficiencies of the various groups of organisms in the soil and 

 whether they are affected by sterilization. I'urther, it is imper- 

 ative to know what role the fungi play in soil fertility, and 

 how they may be taken into consideration when it is desired 

 to have bacteria or protozoa constitute the limiting factor. 

 Finally, a matter demanding immediate study is the actual 

 observation of pure cultures of protozoa acting singularly 

 and collectively upon pure cultures of bacteria, thus furnish- 

 ing some definite basis for the investigations of .soil protozoa 

 as a factor in soil fertility. 



Studies on Heated Soils.— In the Kjix-runrnt 



station. Record (Vol. X.X.iV, No. S; is a note on ttie results 

 of experiments conducted at the University of Wisconsin 

 with the object of investigating the effect of heated soils on 

 plant germination and growth. Most of the seeds experi- 

 mented with were found to be su-cepcible to the iujurious 

 action of highly heated soils. The action apj.ears to be 

 dependent particularly upon the content of organic matter 

 in the heated soil. Different soils gave markedly different 

 results upon heating to the same temperatures, but the extent 

 to which the plant is effected depends upon the degree to 

 which the soil is heated. Approximately 2.50° C. was found 

 to be the most critical temperatuie in all tlie soils used. At 

 this temperature seed germination was most strikingly retard- 

 ed. It is interesting to learu that the ammonia content of 

 the soil increased proportionately to the temperature of 

 heating up to about 250°. Tlie increase in ammonia was 

 accoiiipanied by a decrease in nitrates, which were prac- 

 tically nonexistent in the highly heated soils. It 

 is still more interesting to find that the percentage of 

 seed germination was closely correlated with the amount 

 of ammonia present in the heated soils studied. The 

 amount of ammonia required to injure germination how- 

 ever, appears to vary with the type of soil when comparison 

 of different heated soils are made. The beneficial action of 

 heated soils on later plaat growth, especially soils heated 

 between 160° and 250 , is believed to be due in a large part 

 to the direct assimilation of ammonia and ammonia compounds 

 by the plants. 



The above facts are not without interest in those parts 

 of the West Indies where periods of drought occur causing the 

 soil to be subjected at the surface to high temperatures during 

 the day 



