148 



SCIENTIFIC NEWS. 



[Aug 17, 1888. 



pressure-plate systems. The cut off valves have adjust- 

 ing screws, easy of access, and the matter of adjustment 

 for wear is simple. Besides, any leakage from these 

 valves is excluded from the cylinder at about -f stroke 

 by the main valve, and could not, therefore, result in 

 any serious harm. The valves being, in fact, balanced, 

 will wear but slightly, require very little attention, and 

 never want to be replaced by new ones. 



Another feature of this valve system is of the highest 

 importance. The port openings are doubled for ad- 

 mission, cut-off, and release. This is one of the reasons 

 for the exceptional economy claimed for these engines. 

 A thorough separation of live steam from exhaust is 

 another essential to economy accomplished by these valves. 



Within the casing of the governor is an " inertia 

 wheel," which acts in connection with the ordinary 

 weight and spring forces. This feature is also novel, 

 and produces a very admirable effect upon the action of 

 the engine. The inertia wheel neutralizes the effect of 

 the inertia in the governor weights, and assists the 

 governor in overcoming the resistance of the cut-off 

 valve. The weight and spring forces are made light, 

 and consequently the action is free and rapid. 



Messrs. Fairbanks, Morse, and Co., of Chicago, 111., the 

 makers, are also building compound condensing en- 

 gines, and their performance justifies the prediction that 

 there will be a large demand for them. The saving in 

 fuel by compounding over single cylinder non-condensing 

 appears to be about 40 per cent. ; 2g pounds of coal per 

 horse-power per hour is about what may be expected as 

 the performance of these compound condensing engines. 



THE COLOURS OF FRUITS AND 

 FLOWERS. 



SOME of us assert that the colouring principles of 

 fruits and flowers owe their origin to a process of 

 " natural selection." Others say, or at least said in days 

 by-gone, that these pigments have in each case been 

 mechanically determined by a direct creative act. But 

 each of these explanations merely gives a final cause for 

 their appearance, leaving the efficient cause or causes 

 untouched. Yet surely the most interesting part of the 

 question is to know how, when, and where the various 

 colouring-matters have been formed, and by what agency 

 they have been conveyed to and deposited in those par- 

 ticular parts of plants where we find them, leaving the 

 other parts untouched. We almost fear that the popular 

 study of natural selection has withdrawn attention from 

 these questions. Naturalists have come to think that if 

 they can only show how the development of intense 

 colour in a plant attracts insects and promotes cross- 

 fertilisation the matter is mainly explained, and presto ! 

 the colour must make its appearance. 



We may in the first place remark that brilliant 

 colour, alike in plants and animals, is most conspicuous 

 at the epoch of maturity and in the most intensely 

 vitalized portions of the structure. In plants at least, the 

 distinct pigments hitherto recognised are very few. 

 The white and black shades which we encounter — the 

 latter very sparingly — are not due to any especial 

 colouring-matter. White is due merely to the reflection 

 of light through colourless tissues containing air. Blacks 

 are generally due to the dense concentration of violet 

 pigments. If we set aside chlorophyll green, which, 

 though common in fruits, is rarely met with in flowers, 



we find, according to Dr. A. Hansen, the following three 

 groups : — 1, yellows ; 2, reds; and 3, blues and violets. 



As it was previously demonstrated by Hildebrand the 

 yellows are mostly in combination with the plasmic 

 substance, while the reds, blues, and violets exist mostly 

 in solution in the cell-sap. 



The yellow colouring matter of flowers forms an inso- 

 luble compound with fatty matters, as discovered by Kru- 

 kenberg, and is named lipochrome. This fact goes far to ex- 

 plain the general comparative permanence of the yellow 

 colours both of plants and animals. The yellow pigment 

 obtained by Hansen in a crystalline condition agrees in its 

 behaviour with lipochrome. The spectra of the pigments 

 of different yellow flowers agree with each other so 

 closely as to testify to their mutual identity. Between the 

 F and G lines there occur two absorption bands, which 

 do not occupy exactly the same position. The solutions 

 are not fluorescent. 



Orange is formed by a denser deposit of the yellow 

 pigment. The colour of the rind of an orange is due to 

 the same yellow pigment as that found in the flowers of 

 Ranunculus repens. 



The colour of yellow dahlias and lemon-rind is not 

 lipochrome. It is soluble in water, and behaves differ- 

 ently both chemically and spectroscopically, displaying, 

 for instance, no absorption-bands. It is very similar to 

 the colouring-matter of Aethalium septicum examined by 

 Krukenberg. 



The reds of flowers, in Hansen's opinion, may be re- 

 duced to a single pigment, the dye of roses, carnations, 

 peonies, etc. It is soluble in water, and is decolourised 

 by alcohol, probably in consequence of dehydration. On 

 the addition of an acid the colour is restored. The spec- 

 trum displays a broad absorption-band between D and 

 F. The varying intensity of the colours of roses, 

 carnations, and peonies depends, perhaps, on the presence 

 of acids. The scarlets and brick-reds of poppies, scarlet 

 lilies, hips and haws are doubtless produced by the 

 joint presence of lipochrome. 



The blue and violet pigments also turn pale in alcohol. 

 The solution is reddened by acids, as was noticed by 

 Fremy and Marquardt, who thence concluded that the 

 reds were merely blue pigments modified by acids. 

 Hansen, on the other hand, holds that the blue 

 and the violet colours are modifications of the red. 

 In support of this view he urges the fact that certain 

 blue and violet colours (Boragineae) are at first red. 

 On the contrary, we must remember that the corolla of 

 many fuchsias passes from a bluish violet to a red, 

 whilst the flowers of Erica cinerca open red and turn 

 more to a violet on fading. Salts of iron, added to the 

 soil, turn the red of peony flowers to a violet. Gardeners 

 can also produce blue Hortensias by the use of iron. 

 Peony red is turned to a violet by the addition of sodium 

 phosphate, whilst larger quantities of the same salt turn 

 it blue. The spectrum of the blue and violet pigments 

 has two absorption-bands between D and b. These pig- 

 ments may be combined with lipochrome yellow, thus 

 producing the colour of the berries of Ampelopsis. 

 Hansen assumes, therefore, only four fundamental 

 pigments : — soluble yellow, lipochrome yellow, flower- 

 red, and chlorophyll green. He opposes the view that all 

 colours are derived from chlorophyll green, since the 

 spectra do not agree. 



The view that scarlets in flowers and berries are com- 

 posed of a red pigment superposed upon lipochrome 

 yellow, is strongly confirmed by the instance of bryony. 



