69^ 



^HE TROPICAL AGRICULTURIST. [Amt i, 1886. 



of such Btrong. acids as destroyed or fundameiilally 

 changed it. One thiug Valenciennes conclusively 

 proved, that the pigment contained no copper ; and 

 the viuw which he himself favoured — especially as no 

 proof had heen afforded of the oyster's swallowing 

 the NavicuUu— was that the peculiar colouring matter 

 was nianufaetured by the oyster itself in the intestine 

 and liver, and was thence absorbed and deposited in 

 the gills. The copper theorj', however, was destined 

 to be revived. It was undoubtedly true that a green 

 colour had been fraudulently produced in oysters by 

 the use of copper ; but a still more remarkable fact 

 was demonstrated by Professor Bizio, that a very 

 minute quantity of copper is really normally contained 

 in the blood of the oyster, as in that of otlier molluscs. 

 ■\Vhrther the oyster could take up enough of the 

 metal to be really poisonous is still a matter to be 

 determined by experiment ; but Dr. Ray Lankester 

 holds that the popular notions of oysters or mussels 

 being poisonous when taken from the copper of a ship 

 are mere fallacies. Anyhow, Bizio's theory in no way 

 accounted for the green oyster of Marennes, and the 

 Navicula does so account for it. It was proved, too, 

 that the oyster feeds upon these Naviouja*. Had 

 Gaillou examined the alimentary canal under the micro- 

 scope, he would have found not merely the dark 

 blue-green colour, but the siliceous shells of the diatom 

 in enormous numbers. The way in which the pigment 

 is trar.sferred to the gill filaments is very remarkable. 

 It does not permeate the gills as a whole, but is found 

 localised in a set of peculiar sub-.spherical cells, placed 

 at intervals among the smaller columnar cells of the 

 epithelium. The.se larger cells are " secretion cells," 

 filled with granules, in which the pigment is concen- 

 trated. The granules are probably ultimately disch.-irged 

 as mucin. For the pigment it.self the name Jlarenniu 

 is proposed; it is not really green, but blue, the green 

 colour of the gills being most pronounced when the 

 pigment is diminished in (piantity, and deepenhig to 

 blue as this increases. Finally, the "secretion cells" 

 present some curious phenomena. They are often 

 found sejjarated from their attachments, and crawling 

 like independent creatures, -with slow ami.eboid move- 

 ments, on the surface of the epithelium, "probably," 

 says the author, '■ on their waj» to disintegration, 

 accompanied by production of a mucin-like substance." 

 The singular appearance of these cells, with their 

 long pseudopodia, is well shown in an illustrative plate, 

 which also contains figures, largely magnified, of the 

 diatuins and the gill structures, with a coloured 

 drawing of the green oyster, natural size. There are 

 sundry collateral matters dealt with by Dr. Ray 

 Lankester. of considerable interest, for which we must 

 refer to the paper itself. — Field. 



MAHWA FIjOWERS. 



Attention has been publicly drawn of late to "Mahwa 

 Flowers " — the corollas of Bas-tia latifofia — as a cheap 

 source of cane-sugar. This species of Bassia is a tree 

 attaining to a height of 40 to 60 feet, and common in 

 many ])arts of India, especially in Central Hindustan. 

 It has oblong leaves of firm texture, from 5 to (i inches 

 long ; these fall in February, March, or April, and are 

 (succeeded in March or April by the flowers. These 

 ^a^t for tv'o or three weeks and then begin to fall. 

 The fall takes place at night, and continue eometiraes 

 for a fortnight. The fruits, which resemble a small 

 apple, ripen in three months ( the seeds, one to four 

 in number, yield an edible oil by pressure. It should 

 be atided that the trees are self-sown, and that they 

 fiourish in very poor and stony soil. 



When the Jlahwa tiee is in bud, the ground be- 

 neath it is cleared of weeds, sometimes by burning, 

 A single tree may yield as much as six to eight 

 niaunds* of flowers; even thirty mauuds have been 

 asserted to have been collected from one tree. These 

 flowers have a luscious but peculiar taste when fresh ; 

 when dry they res< mble in flavour inferior figs. 

 They form a very important addition to the food of 

 frhe poorer classes in those districts where the tree 



*A Bengal maiuid equ»l« 82^ lb. sroirdupoii^ 



abounds, particularly in the neighbourhood of wood- 

 lands and jungles. They are specially useful in eco- 

 nomising cereals in seasons of famine and drought. 

 They are sometimes eaten fresh, but more commonly 

 sun-dried, and are usually consumed with rice and the 

 lesser millets, or with seeds of various kinds, and leaves. 

 It is said that a man, his wife, and three children 

 may be supported for one month on two maunds of 

 Mahwa flowers. * 



It is not, however, as a direct article of food, nor 

 as a material for the preparation of a raugh spirit 

 by fermentation (a very common use ot these flowers) 

 that Mahwa blossoms are now recommended. It has 

 been aflirmed that they may be employed as an abund- 

 ant and very cheap source of cane-sugar. In the 

 Morning Poft ot October 1.5, 1885, appeared an article 

 on this subject, in which it was stated that, " If the 

 Mahwa flowers be available in sufficient quantities for 

 the sugar-makers of Europe, there can be no question 

 that the days of the beetroot are over, and sugar- 

 cane will go the way of all discarded products." This 

 prediction depends, however, upon another condition 

 besides that of the abundance of the flowers. It the 

 sugar they contain be wholly or chiefly cane-sugar, 

 that is, " sucrose," then the argument is not without 

 weight. But the nature of the saccharine matter of 

 the Mahwa does not appear to have been ascertained. 

 MM. Eiche and Kemont (Journ. de Fliarm. ct Chimie, 

 1880, p. 215) stated that the air-dried flowers contain 

 60 per cent of fermentable sugar, of which about 

 one-seventh is crystallisable. The material available 

 for analysis in Europe consists, of course, of the dried 

 flowers. These may have suffered some change beyond 

 the mere loss of water, but the evidence they afford 

 on chemical examination is not favourable to the view 

 that they are likely to compete with sugar-beet or 

 sugar-cane as a source of cane-sugar. Here is the 

 i-esult of an analysis of a sample of Mahwa flowers 

 (from the Kew Museum) in their air-dried con- 

 dition : — 



In 100 parts 



C»ne-.sugar 3-2 



Invert-sugar 526 



Other matters soluble in water ... 7'2 



Cellulose 2-4 



Albuminoids ... ... 2"2 



Ash 4-8 



Water lost at 100° 15-0 



Undetermined 126 



The flowers analysed had a slight smell of fermented 

 csachariue matter and a distinct acid reaction. But 

 it is not at all probable that they could have con- 

 tained any large proportion of cane-sugar even when 

 guite fresh, and that 15/16ths of that .-^ugar had been 

 inverted during the process of desiccation. We can- 

 not argue from analogy in this case. For while the 

 nectar of many flowers contains no sugar except 

 sucrose, invert-sugar occurs in some blossoms, as well 

 as in many other parts of plants. Even the unripe 

 and growing stems of (lie sugar-cane and of many 

 grasses contain much iuvcrt-.sugar. It must, however, 

 on the other liHiid, be remembered that cut sugar-canes 

 imported into this country couiain a large amount 

 of invert-sugar, and that if they be kept a week mily 

 after the harvest the invert-sugar naturally present 

 in the juice shows a marked increase and the caue- 

 sugar a corresponding diminution. On the whole, then, 

 .so far as the materials at my disposal enable me to 

 judge, I believe that the saccharine mitttr of fresh 

 Mahwa flowers will be found to consist mainly of 

 dextrose and levulose, and that consequently they will 

 not be available as a material for the economic pro- 

 duction of sucrose. 



I have to thank Mr. M\ T. Thiselton Dyer, C.M.G., 

 Director of the Koyal (Jardi^ns. Kew, for drawing my 

 attention to this subject, and for a supply of the 

 material on which I have worked. — A. H. Chijech. — 

 Xaturc. 



*For an interesting account of the Mahwa tree and 

 its products, see a paper by E. Lockwood in the 

 Jouninl of the Lianeao Society ("Botany"), vol ivii, 



pp, s7-yy. 



