Vol. IX. No. 218. 



THE AGRICULTURAL NEWS. 



the plant is grown under the dry conditions prevailing in 

 many parts of the mainland of South Anierii-a, than when it 

 is cultivated under the moist condition:< of certain of the West 

 Indian Islands. Again, Madden, in a pajier communicated to 

 the Koyal Society of London in 1731, drew attention to the 

 fact that cherry-laurel water, prepared l>y distilling water in 

 which bruised cherry-laurel leaves had been macerated, was 

 poisonous. The latter case was also e.xjilained by Schnider 

 in 1803, as being due to the production of prussic acid. The 

 cases of bitter almonds and cherry-laurel leaves remained 

 until about 18.51 practically the only known instances of the 

 production of prussic acid by plants, but since that year the 

 formation of this acid has been detected in a very large 

 number of plants, and in an incomplete list of such plants 

 recently compiled by Dr. Greshoff, of the Colonial Museum 

 at Haarlem, about 150 species are enumerated. In most of 

 these cases, investigators have been content to record the fact 

 that prussic acid is produced, and the method of its produc- 

 tion has been definitely ascertained in comparatively fe»v 

 instances. 



In all the plants in which the chemistry of cyanogenesis 

 has been thoroughly investigated, it has been found that the 

 prussic acid is liberated when the plant is ground up, either 

 in its fresh, moist condition, or if it has been previou.sly dried, 

 when the dried ground plant is placed in water: in every case 

 the presence of water is essential. It has also been found 

 that from all such plants, by appropriate methods, a liefiiiite 

 crystalline compound can be isolated, which is quite stable, 

 and can be kept for indefinite periods, but which when dis 

 solved in water and boiled with dilute a<-ids decomposes and 

 evolves prussic acid. This same decomposition with the 

 production of pru.ssic acid, can also be brought about by 

 various ferments. This may jierhaps be conveniently illus- 

 trated by an example. I'y extracting bitter almonds with 

 alcohol, a colourle.ss crystalline substance can be obtained, 

 which has been named amygdalin. When a solution of the 

 latter in water is boiled with diluted hydrochloric acid (s[iirit 

 of salt), the mixture acquires the well kmiwn odour of essence 

 of bitter almonds, owing to the fact that jirussic acid ami ben- 

 zaldehyde (oil of bitter almonds) are simultaneouslj' produced. 

 The same decomposition is brought about if ordinary yeast 

 is added to a solution of amygdalin in water. It may be 

 assumed, therefore, that this crjstalline substance, amygdalin, 

 is the source of the pru.ssic acid and the oil of bitter 

 almonds, which are formed when ground bitter almonds are 

 mixed with water. The agent contained in the bitter almond.s 

 which eflfeots this natural decomposition of amygdalin Iris 

 been found to be a special ferment. The latter, like amygdalin, 

 can be isolated from bitter almonds, and is prepared and sold 

 under the name emulsin. The proof that the production of 

 prussic acid in the bitter almond is due tn the decomposition 

 of amygdalin by emulsin, is found in the fact that the additii>u 

 of emulsin to amygdalin, dissolved in water, results in the 

 almost immediate production of prussic acid and oil of bitter 

 almonds. 



Amygdalin belongs to a well-defined class of substances 

 known to chemists as glucosides; the latter name indicating 

 that when they are decomposed in the way already indicateil 

 by acids or ferments, they invariably yield glucose or 

 a similar saccharine substance, in addition to certain more 

 specific products such as the prussic acid and oil of bitter 

 almonds produced in the case of amygdalin. These gluco- 

 sides may be divided into two cla.sses, according as they do or 

 do not yield prussic acid on decomposition, and it is convenient 

 to describe the former class as cyanogenetic glucosides. The 

 (ermentive agents which accompany these glucosides in 

 plants, and which serve to decompose them, are termed 



enzymes or unorganized fernient.s, the latter name serving to 

 distinguish them from the organized ferments such as yeast, 

 mould, etc. Itecent researches have shown that enzymes are 

 widely distributed in plants and animals, and that many of 

 the functions necessary to life are discharged by them. 

 A general article on organized ferments and their industiial 

 application has already been published in the Bulletin 10C5, 

 3185, to which reference may be made for fuller information. 

 (From the Bulletin of the Inijieriol Iiixtitute, Xn]. IV, p. 329.) 



THE FERTILIZING INFLUENCE OP 

 SUNLIGHT. 



On page 107 of the current volume of the Agricultural 

 Xews, extracts were given from a letter in iV«^u/e of February 

 17, 1910, signed by A. Howard, Imperial Economic Botanist, 

 India, in which it was pointed out that the custom of expos- 

 ing the soil to direct sunlight for some time, which obtains in 

 parts of India, for the purpose of increasing its fertility, may 

 possibly have some connexion with the experiments of Russell 

 and Hutchinson, which have shown that the partial steriliz- 

 ation of soil may have some etlect in increasing its product- 

 iveness. These experiments were dealt with in the editorials 

 of Xos. 202 and 203 of the Aijrieulturfd News, to which 

 reference is made. 



Following on the letter mentioned, several have been 

 published sub^^equently in Nature which increa.se the interest 

 of the subject. In the i.s.sue of that journal for March 3, 1910, 



E. J. Rus.sell, one of the experimenters referred to above, 

 supports the view that direct sunlight may have some steriliz- 

 ing influence which increases the productivity of the soil, 

 much in the same way as this is done by the action of heat 

 and antiseptics. This is by reducing the numbers of the 

 larger soil organisms which feed on the bacteria, so that 

 the nitrogen-fixing organisms have the best chance to .sur- 

 vive, with the result that they increase largely in numbers, 

 and their effect in adding nitrogen is much greater than in 

 unsterilized .soil. Further, it is suggested that, as climatic 

 difficulties interfere with the making of experiments in con- 

 nexion with the subject, in England, a series of these should 

 be conducted in Indiu, where circumstances are more favour- 

 able. 



Another letter, in the issue oi Nature iov "Slaxch. 10, 1910, 

 makes reference to the increase of soil fertility that is gener- 

 ally evidenced where waste vegetable matter has been burned, 

 and this is followed by another, in the issue of March 24, 

 1910, drawing attention to the larger crops that are obtained 

 from soil into which steam has been injectad for the purpose 

 of destroying various pests. 



Returning to the subject of the fertilizing influence of 

 sunlight. Nature for April 7, 1910, contains a letter from 



F. Fletcher, of the Bombay Agricultural Department, which 

 suggests that the ett'ect of the sunlight in increasing productive- 

 ness is due to the destruction of some toxin contained in the 

 soil. This supposition is dealt with in a letter in the issue of 

 April 28, 1910, in which Russell refers again to the experi- 

 ments that have been conducted by himself and Dr. Hutchin- 

 son, stating that this hypothsesis was the first examined by 

 them, but that it was found insufficient to explain the 

 phenomenon. He points out that, as the addition of 

 a watery extract of untreated soil to soil that has been 

 partially sterilized by toluene causes a further increase in 

 fertility and bacterial activity, it is made difficult to 

 maintain that ordinary soils contain toxic substances which 

 reduce the number of the bacteria, and that the effects of 

 sunlight or partial sterilization is to remove these. 



