850 . REPORT— 1897. 



and Wilfarth showed in 1888-90 that, provided the root-nodules are present, these 

 leguminous plants fix the free nitrogen of the atmosphere ; and Laurent and 

 Schloesing put this beyond all doubt in 1892 by demonstrating that a closed 

 atmosphere in which Leguminosee grow loses nitrogen in proportion as the plants 

 gain it. Meanwhile Schulz Lupitz had shown that agricultural land poor in nitrogen 

 can be made to accumulate it in paying quantities by growing lupines on it, and 

 quite recently pure cultures of the organism of the nodules have been placed on 

 the market under the unfortunate name Nitragin. It is claimed that these organisms 

 can be readily used in practice to inoculate the seeds or soil. 



Kossowitsch in 1894 showed that certain symbiotic unions of algss with bacteria 

 are also capable of fixing nitrogen ; and Winogradsky declares that there exists in 

 the soil a bacterium which, provided it is kept protected from oxygen by aerobic 

 soil organisms, can itself do this. We are quite unaware of the mechanisms here 

 concerned ; but in all cases it appears certain that active destruction of carbohy- 

 drates is an essential condition, and we can only assume that the nitrogen is forced 

 into synthetic union by means of energy derived from this destruction. Here, 

 then, we have a glimpse of the up-grade part of the cycle of nitrogen in Nature, 

 the importance of which to agriculture cannot be overrated. As to the theoretical 

 bearings of the matter, we are still much in the dark, and can only anxiously await 

 the results of further investigations into the nature of the peculiar fermentations 

 and their products going on in these nodules. 1 now want to draw your atten- 

 tion to a bearing of the above discoveries concerning denitrifying bacteria on some 

 agricultural and horticultural questions. 



It is well known that a gardener eschews the use of fresh manure. Why is 

 this ? The most obvious reply might seem to be, because the ammonia compounds 

 and other nitrogenous constituents in such manure are not directly useful, or are 

 even harmful to the roots of the plants. Some recent researches suggest that the 

 matter is more complex than this. 



It has not unfrequeutly happened that a farmer, finding himself short of stable- 

 manure, has made up the deficit by adding some such artificial manure as Chili 

 saltpetre, his argument running somewhat as follows: — Both are good nitro- 

 genous manures, the one acting slowly, the other rapidly, so that a mixture of both 

 should be better than either alone. The results have disappointed him, and 

 numerous experiments in Norfolk, as I am informed by Mr. Wood, and in the 

 North of England, as Dr. Somerville assures me, have shown that most disastrous 

 results ensue if such mixtures are used, whereas if the farmyard manure is em- 

 ployed at first — the ' shorter ' the better — and the nitrates applied later on as a 

 * top-dressing,' excellent crops follow. The explanation seems to come from some 

 recent experiments hy Wagner, Maercker, Burri and Stutzer, and others. The 

 farmyard manure, especially if fresh, so abounds in denitrifying bacteria that they 

 destroy the nitrates rapidly and completely, free nitrogen escaping. Curiously 

 enough, a very active denitrifying bacillus was found on straw, and we know 

 that straw abounds in such manures. 



I did not intend to go so far into agricultural details as this, but it was impos- 

 sible to resist these illustrations of the splendid field of mycological research which 

 here lies before us. 



Nor can I avoid instancing at least one more example of the organisms at work 

 in manure. We all know what enormous quantities of cellulose are manufactured 

 daily, and even hourly, by the activity of green leaves ; and when we reflect on 

 the millions of tons of dead-wood, straw, fallen leaves, roots, &c., which would 

 accumulate every year if not destroyed, we see at once how important is the 

 scavenging action of the moulds and bacteria which gradually reduce these to 

 carbon-dioxide and water, setting these gases free to enter once more into the 

 cycle of carbon, oxygen, and hydrogen in Nature. 



In 1890 Van Senus obtained two bacteria, one an aerobic and the other an 

 anaerobic form, which in symbiotic union were found to excrete an enzyme which 

 ■dissolved cellulose. Such a cellulose-dissolving enzyme I had myself isolated from 

 the Botrrjtis of the lily-disease in 1888. In 1895 Omeliansky, working with 

 river mud, found an anaerobic bacillus which dissolves paper with remarkable 

 rapidity. I can only hint at the importance of these forms in connection with the 



