Vol. IV. No. 86. 



THE AGRICULTURAL NEWS. 



229 



SCIENCE NOTES. 



Roots of Cotton Plants. 



Mr. J. R. Uovell, F.L.8., F.C.S., and Mr. Thouiiis 

 Thornton, A.R.C.S., have been carrying out investiga- 

 tions at Barbados with regard to the character of the 

 roots of the cotton phmt. 



In reporting some very interesting results they 

 state : — 



The roots of plant.s examined havL been measured, and 

 the average depth to which the primary roots penetrated 

 was 19 inches, the maximum being 24 inches, and the 

 minimum 14 inches. 



The secondary roots commenced on the average to be 

 put off at 3'4 inclie.s below the surface of the .soil, the 

 maximum being 5 inches, and the mininuim 1'.3 inches. The 

 secondary root.s were, on the average, traced to a distance of 

 45 inches ; the maximum being 63 inches, and the minimum 

 39 inches. The longest secondary roots, at some distance 

 below the surface of the soil, were on the average 11 inches 

 deep ; the maximum being LS inches, and the minimum 

 8 inches. They were traced horizontally on the average for 

 31 inches ; the maximum being 48 inches, and the minimum 

 18 inches. 



Soil Inoculation for Legumes. 



The following review of a recently issued bulletin 

 (No. 71) of the Bureau of Plant Industry of the 

 U. S. Department of Agriculture, by Dr. G. T. Moore, 

 entitled ' Soil inocidation for legumes,' appeared in the 

 Botivnical Gazette for June: — 



The subject of soil inoculation for legumes has recently 

 acquired a wide-sjn'ead interest in this counti-y, first from 

 numerous popular accounts relating to the subject, and again 

 on account of a widely advertised commercial product by 

 which, it is claimed, the pro[ier bacteria can be introduced 

 into the soil. For this rea.son Moore's account of his work 

 in this field is of .special interest. The first part of the 

 bulletin is a general historical account dealing with the 

 various methods by which nitrogen is fixed in the soil, and 

 leading up to the discoveries of Helriegel and Willfarth 

 connecting the fixation of nitrogen by legumes with the 

 tubercles on the roots, and the discovery of bacteria in these 

 tubercles by AVoronin. The chief results of Jloore's investi- 

 gations may be briefly stated as follows: The root-tubercle 

 organism exists in three well-defined forms. In the soil it 

 has the form of extremely minute motile rods. These 

 possess the power of infecting the root hairs of leguminous 

 plants. Within the root the organisms nudtiply enormously 

 and produce the hypha-like ' infection threads ' [lassing 

 through the tissues of the host. These curious fungus-like 

 structures have often been observed and figured, and have 

 been the objects of nuich discussion. Their explanation is that 

 they are zooglaea-masses composed of numerous minute bac- 

 teria. These minute bacteria soon give rise to larger rod- 

 shaped forms which may or may not be motile. These finally 

 produce tlie branched forms peculiar to the legume nodule. 

 It is only this last form that is of any benefit to the plant.s, 

 for in this state the bacteria are broken down, and their 

 contents made available. The name of the organism is 

 changed to I'seuJomonas rndlctcola, since the motile rods 

 have flagellae only on one end. There is only a single 

 species, but several forms or races occur adapted to certain 

 species of legumes. Their .slight racial characteristics may 



be easily broken down by cultivation. The results of 

 studies on the nitrogen-fixing power of the bacteria are 

 extremely interesting, showing that the supposed symbiotic 

 relation between the organism and the root probably does 

 not exist. It is rather to be regarded as a parasite, its 

 nitrogen value being merely incidental to the death of the 

 organism. The nitrogen is fixed by the tubercle-forming 

 bacteria within their bodies. This was determined by 

 cultures in flasks containing nutrient solutions without 

 nitrogen. There was no increase of nitrogen in the solution, 

 but a marked increase in the organisms themselves. In its 

 biology the organism is therefore considered a parasite. 

 Later the [ilant is able to overcome the parasite and profit 

 by the nitrogen which has been fixed. When grown on 

 nitrogenous media, it was found that the organism lost both 

 its power of infecting leguminous plants and its power of 

 fixing nitrogen. In non-nitrogenous media both of these 

 properties were retained. The failure of Nobbe's attempts in 

 Germany, a few years ago, to put upon the market pure 

 cultures of this organism can probably be attributed to lack 

 of recognition of this fact. As a result of these studies 

 Moore has devised a method of putting up for distribution 

 piu'e cultures of r^eudoiiKjit.as radicicola, grown in nitrogen- 

 free media and dried on cotton immersed in the culture. 

 These cultures are sent out by the U. S. Department 

 of Agriculture together with packages of nutrient salts to 

 multiply the organism. 'I'lie mas.s-culture thus obtained is 

 used to inoculate the seed or the soil. Numerous reports 

 from farmers of all states indicate that this method will 

 prove successful and jiracticable. 



ARTIFICIAL DRYING OF CACAO. 



In his article on 'Grenada at the Colonial Exhibi- 

 tion,' in the West India Committee Circular, from 

 which extracts are given elsewhere in this issue, 

 Mr. W. G. Freeman makes the following observations 

 on the artificial drying of cacao. Mr. Freeman refers 

 to the cacao drier erected by Mr. Hoadley, which was 

 described in the Ag vie ult aval iVew.s, Vol. IV, p. 174: — 



The cacao exhibit, although not extensive, is of great 

 interest, because, like the nmch larger display of Trinidad, it 

 is indicative of the progress which is being made in agri- 

 cultural methods in the West Indies. The two samples of 

 pea.sant-cured, sun-dried cacao represent the old order of 

 things, whilst the new order is represented by the bag of 

 cacao exhibited by the Hon. D. S. deFreitas, from Dougald- 

 ston estate. As the label in the court states, this cacao was 

 placed direct from the fermentation boxes into one of the 

 cacao-drying machines manufactured by Messrs. J. Gordon 

 & Co., and completely dried and polished, without breakage, 

 in twenty-four hours. The Cjuality of the product is made 

 evident by the fact that the sample exhibited gained the first 

 prize at the recent Agricultural Show in Grenada. This 

 sample, and that in the Trinidad court, dried in ilr. J. 

 Hoadley's machine, are worthy of the serious consideration 

 of all cacao producers. The cultivator in temperate climes 

 has long been forced to recognize that old methods must be 

 replaced by new if he is determined to hold his own in the 

 struggle for existence. In the tropics, owing to special 

 circumstances, this necessity has not yet been so universally 

 brought home, but here also increasing competition must 

 inevitably result in success falling only to those who by 

 taking advantage of each improvement turn out produce of 

 high and uniform quality, by the most economical and up-to- 

 date methods. 



