904 



THE TROPICAL AGRICULTURIST, 



[JUITE 2, 1884, 



having a pair of long appendages at the side of the abdomen, 

 which are attached to the Btigmata, and iJiohably protect 

 them from the bro-ivn, sticky pulp within the fruit. 



Paul JIayer has investigated the wasps of numerous 

 other old-world species of Figs, mostly from herbarium 

 specimens. In some species of Ficus and Sycomorus he 

 has found Blastophaga and Sycophaga together, but the 

 whole number of species of wasps was very small. On 

 the other hand, the Brazilian Figs, of which Fritz Muller 

 examined ten species in his own neighbourhood (Blumenau, 

 province of St. Catharina), possess an astonishing variety 

 of wasps belonging to the same family of the Agaonidm ; 

 some of these lielong to the genus Blastophaga, some to 

 the genus Uke Ichneumon. Many are adorned with metallic 

 colours, which fact suggests a longer stay in the open 

 air. In point of fact, most of the Figs which Fritz Muller 

 studied flower only once a year, so that many of these 

 wasps must, in order to lay their eggs, seek another free 

 of the same species which is just beginning to flower at 

 the time when the Figs are ripe upon the tree where 

 they themselves were developed. In the case of many 

 species of these wasps, at least four migrations are necessary 

 in the course of the year. 



In these Figs, the only inflorescence from which the 

 wasps issue bears only male flowers, and the young in- 

 florescence, which they enter, bears only female flowers. 

 Self-fertilisation is thus rendered impossible, and separate 

 individuals are regularly crossed. The fruit becomes sweet, 

 and in many cases gaily coloured, when the seeds ripen, 

 and parrots, which feed on it, help to disseminate the 

 seeds.^Produce Ilarkets' Eeviev:. 



NEW RESEARCHES ON THE APPLICATION OF 

 SALICYLIC ACID IN THE MANUFACTURE ■ 

 OF CXS'E AND BEET SUGAR. 



Some new and important investigations have been carried 

 on in various parts of the world, during the last few yeais, 

 with regard to the value of salicylic acid in the manufact- 

 ure of sugar from the sugar cane or beet root, and we pro- 

 pose to say a few words about them here. 



The first problem of importance that had to be solved 

 was that relating to the cmise of the prodiictinn of glucose 

 in solutions of sugar or in cane juice. It has been long 

 suspected that some organic acid was the cause of this 

 transformation, so deleterious to the sugar-boiler by the 

 large amount of molasses which resulted from it, and that 

 was the origin of the introduction of lime as a defecator. 

 This lime not only collected the scum and precipitated tannin 

 compounds, etc., but neutralized any organic acid which 

 might be present. 



Now, although it has been long shown by actual experi- 

 ment in the laboratory that acids of all kinds boiled with 

 solutions of cane sugar will convert it into glucose, it ap- 

 pears very probable, in fact certain, that nciih present in 

 the juice' are nut the chief cause of conversion, if indeed thcg 

 are, in this instance, a cause at all. It is now some years 

 since Dr. Phipson first hinted that mtcj'o-organisms might 

 be the origin of the inversion of sugar in the boilers of the 

 West Indian plantations, and that this cause, so detrimental 

 to the interests of the sugar producers, might probably be 

 done away with by a judicious use of salicylic acid. His 

 coujectm-es have since been fully verified by the discovery 

 of the inverting micro-organisms in the moist sugar of the 

 AVest Indies, and in the unrefined product of the beet root. 

 They have been detected and isolated ; moreover, they have 

 been cidtivated in appropriate media, and their action on 

 the cane sugar (saccharose) fully investigated. 



As might have been anticipated, this action is found to 

 depend, to a great extent, upon temperature. At a low 

 temperature the micropbytts of raw sugar solutions are 

 more or less inactive ; but at the high temperature which 

 constantly prevails iu our West Indian colonics they are 

 ^n full play, and convert cftne sugar very rapidly into 

 glucose, that is, in plain language, ci-ystalline sugar into 

 molasses. 



According to some recent researches by Professor Gayon 

 on the sugars of Guadaloupe, Mauritius, and other places, 

 it appears well proved that the production of glucose in 

 raw sugars is increased h-fhcat and moisture. What is known 

 as -'fermentation temperatuie " is a very appropriate 



degree of warmth for rapidly promoting an increase of 

 glucose ; moisture is also a very favourable condition f < r 

 its production. It is also found that when sugar is stored 

 in large heaps, glucose increases from month <to month, 

 until it atta,ins to very considerable amounts. 



Let us mention as a curious fact, en passant, that one of 

 the micro-organisms isolated from raw sugars is known to 

 naturalists as JIucor circinelloides, and possesses the singular 

 property of causing the transformation of glucose into 

 carbonic acid and alcohol, but is not capable of affecting 

 saccharose or crystalline cane sugar itself. When a mixture 

 of cane sugar and glucose is submitted to the action of 

 this peculiar kind of mildew, it acts upon the glucose and 

 destroys it without converting any of the cane sugar. 



Four or five distinct species of microphytes have been 

 isolated from raw cane sugar besides the one just alluded to ; 

 it is only the jjurest refined sugar that is totally exempt 

 from them; and it is now generally admitted that their 

 presence is quite sufficient to account for the gi'adually in- 

 creasing production of glucose in raw cane sugars and in 

 cane juice. This has. in fact, been proved by a number of 

 direct experiments, in which the inversion was found to 

 increase with the abundance or activity of the; ferment added 

 to solutions of pure sugar. Much interesting information on 

 this subject is contained in Professor Gayon's little pamphlet, 

 Rechei'ches sur la Formation dn Sucre reducteur, published at 

 Paris iu 1881. 



With regard to the application of salicylie acid to neutral- 

 ise the effects of these microphytes in the sugar-vats, Dr. 

 Phipson originally proposed a minute quantity (say 1 part 

 for 10,000 parts of sugar) to be used along with the defec- 

 ating Ume, but to be added to the juice before the lime, in 

 fact, the moment the juice left the mills. This instruction 

 appears to have been misunderstood : the juice was allowed 

 to be heated after the addition of the salicylic acid ; and 

 before the lime was added to neutralise the acid by forming 

 salicylate of lime, a certain quantity of glucose was already 

 formed. Professor Gayon proposes, on this account, to use 

 salici/late of soda in place of salicylic acid, but it is question- 

 able whether the salicylate of lime would not prove the more 

 advantageous. 



Experiments made in test-tubes, in which salicylic acid 

 and solutions of cane sugar were heated to boiling jjoint in 

 the proi^ortion of 1 of salicylic acid to 1,000 of cane sugar, 

 produced a notable amount of glucose iu the course of two 

 hours, but this is ten times the amount of glucose origin- 

 ally proposed to be used. It is probable, however, that 

 pure salicylic acid could not be advantageously employed, 

 unless Dr. Phipson 's proposition of neutralising it (immedi- 

 ately before heating) by the addition of lime was pro- 

 perly carried out. 



Fortunately the saline compounds of salicylie acid are 

 almost as powerfully disinfectant or anti-parasitic as the 

 pure acid, and they have, moreover, the advantage of being 

 very much more soluble in water and solutions of sugar. 

 Professor Gayou's experiments place sahcylate of soda^iXhe 

 very top of the list of the many antiseptics tried for 

 arrestinfj the development of glucose m solutions of cane sugar. 

 It has been found that 2 parts of salicylate of soda for 

 10,000 parts of pure sugar are sufficient to check the pro- 

 duction of glucose, and this check corresponded precisely 

 with that *'f the development of the microphytes. Sugar 

 solutions which gave one to two microphyte cells in the field 

 of vision I cfore the experiment, were left for a fortnight, 

 one-half of the solution having received 2 parts of salicylate 

 of soda tor 10,000 parts of sugar, and the other half contain- 

 ing nothing but sugar and distilled water. At the end of 

 the fo! tuight the latter showed 15. to 2.5 micaophyte cells 

 per ficUI. whilst the half containing nothing but sngar 

 and di.-tilled water. At the end of the fortnight the latter 

 showed 15 to 25 microphyte cells per field, whilst the half 

 treated with salicylate of soda gave one to two cells as he- 

 fore. The original sugar contained 2'S3 of glucose, the 

 solution in distilled wat«r, after a fortnight, showed 6'98 

 per cent, and that containing salicylate of soda S'O.O per cent. 

 This experiment .speaks for itself, and its importance wiU 

 be at once understood by all sug.ir makers. 



Experiments with salicylate of lime have not yet been 

 made, but it is possible the results may be still more ad- 

 vantageous, as a lime salt would be preferable to a so 'a or 

 a potash salt, being less liable to prove injurious in the ulterior 

 processes. But when we consider the extremely small 



