ROOT-NODULES OF LEGUMINOSAE. 133 



land contains bacteria of a less degree of virulence than those sent out in the Department cultures an 

 inoculation is worth while." 



The organism is named Pseudomonas radicicola (Beyr.) Moore. Sometimes it may be present 

 abundantly in roots which show no nodules, e. g., in berseem and in alfalfa. Suspected also to have 

 been present once in this way in soy-bean and once in white lupin. 



At Dr. Moore's request the chemists of the U. S. Department of Agriculture made nitrogen 

 determinations from many of his flask cultures. These experiments are not given in detail but only 

 referred to in a general way. The culture medium consisted of mag. sulphate, potassium phosphate, 

 and maltose in water, and preliminary determinations showed per 100 cc. only 0.0003 gram of nitrogen 

 (as nitrite). After inoculation, air was drawn through the flasks (90 in all) by an aspirator, after 

 first passing through a flask filled with pumice stone and sulphuric acid. 



The actual gain in nitrogen in the inoculated flasks at the end of the third week varied from 

 0.0002 gram to 0.0022 gram per 100 cc. 



"The checks or uninoculated flasks of which there were twelve, four being analyzed at the end 

 of each week, at no time showed an increase over the original 0.0003 gram per 100 cc." 



It is not stated whether these also were aspirated. 



A second series of flasks was started some weeks later to determine whether the increased nitrogen 

 was combined with potassium in the fluid or was contained in the cells of the bacteria. After some 

 weeks' growth the filtrate and fluid were analyzed separately, the results showing that most of the 

 nitrogen was held in the bacteria themselves. 



It is also stated that "Analyses of the nodules of legumes show that they frequently contain as 

 high as 7 to 8 per cent of nitrogen, while other parts of the plant will not possess more than 2 per 

 cent." It is not stated what other parts were compared, i. e., whether equally young parts which 

 would make a very great difference. 



"The large rods will withstand desiccation for a year or more, and, therefore, because they may 

 be sent dry any distance and upon being revived be in the same condition of efficiency with which 

 they started, the problem becomes a very simple one." 



The probability, however, is that the problem is much more complex than here supposed, 

 although the writer of this book must continue to believe that many of the cultures sent out on 

 cotton were virulent. 



Owing to criticism of various workers at home and abroad who declared the method to be 

 worthless, the Department of Agriculture soon abandoned distribution of the organism on cotton, 

 and now sends out its pure cultures sealed in glass tubes suspended in fluid. 



In this connection, however, see favorable comment under Peglion (1905) in Literature. Of the 

 2,502 reports received by Dr. Moore from growers 1,296 reported an increase in crop on the inoculated 

 part of the field, or on the whole field as compared with previous years, and not a few of the reports 

 were extremely favorable, the following for example : 



" On 53 untreated vines [peas] , taken as they came, I found 102 pods; on 53 treated vines taken 

 as they came in the next row, I found 856 pods. The first picking well-nigh stripped the untreated 

 row; the treated ones have yielded two good pickings since, and still another is now filling out." 



Kruijff's criticism (1907) is as follows: The root-nodule bacteria of leguminous plants will not 

 withstand drying upon cotton for any great length of time, and this method introduced by Moore 

 is worthless. The fluid prepared in the manner directed by him, i. e., with the packages of ammonium 

 phosphate and sugar, and inoculated with the cotton received from America clouded, it is true, but 

 a microscopic examination showed that the micro-organisms in it were mostly other than the nodule 

 organism. Once it consisted almost entirely of yeasts. Streaks on agar made from distilled water 

 in which the cotton had been soaked gave only rare colonies of the organism. The appearance of 

 the other organisms is attributed to careless preparation of the cotton. Because it was believed that 

 the virulence of the organism on the cotton from America had been increased by its method of 

 cultivation, they were very anxious at Buitenzorg to try it. Inoculations were, therefore, made 

 from the colonies obtained on the agar streaks, but with no favorable result. In two cases out 

 of six an increased yield was obtained but with bacteria isolated in Java. The increase in one 

 case was 15 per cent (grown on Hiltner's media) and in the other 17 per cent (grown on Moore's 

 nitrogen poor agar). Soy-beans were used for the first mentioned experiment and Katjang tjina 

 (peanut?) for the second. 



Harrison and Barlow in Canada have recently published on this subject (1907). 



They examined the roots of 30 foreign economic species of the suborder Papilionaceae, 24 species 

 and varieties of Vicia, etc. Nodules were found on the roots of all with the exception of Cicer 

 arietinum and Galega officinalis. In the suborder Caesalpineae they examined the roots of Gymno- 

 cladus, Gleditschia, Cercis canadensis and no nodules were found, mycorrhiza, however, were present 

 in all cases. 



