Jan. 27, 1888.] 



SCIENTIFIC NEWS. 



85 



dent. While standing near a pond on his estate, a 

 gentleman at Worcester observed a weasel give chase to 

 a frog, which it followed to the water and succeeded in 

 capturing. Holding it firmly by the head, the weasel 

 emerged from the water and brought its victim to the 

 bank, but on finding itself disturbed let go the frog and 

 disappeared. Happening to visit the spot on the suc- 

 ceeding day, the gentleman found the frog alive in exactly 

 the same place where it had been left by the weasel, 

 although it had been bitten through to the skull. — ■ 

 Nature. 



Luminous Bacteria. — Three new kinds of luminous 

 bacteria have been described by Dr. Katz, in a communi- 

 cation to the Linnean Society of New South Wales : 

 Bacillus Argeuleo-p/iospiiorcscens, I., 11., and III. All 

 three give off" a fine silvery light. No. I. liquefies gela- 

 tine, which II. and III. do not. 



Memory of Wasps. — From some experiments made by 

 G. W. and E. G. Peckham, and described in the American 

 Naturalist, it would seem that wasps remember the 

 locality of their nests for ninety-six hours. 



Physiological Selection. — Professor G. J. Romanes, 

 writing in iV^/;/;r,.does not see how Mr. Seebohm can re- 

 concile his doctrine of a pre-ordained or teleological varia- 

 tion with his theory of the paramount influence of geo- 

 graphical isolation. Mr. Wallace, having argued in favour 

 of collective variation, z.c, oL a considerable percentage of 

 identical and beneficial variation arising simultaneously 

 in the same community, Mr. Seebohm replies that by 

 the admission of this fact Mr. Wallace has dethroned his 

 own theory of natural selection from its position as the 

 main factor in the origin of species. 



The Leaps of Hares. — Mr. R. W. Shufeldt com- 

 municates to Nature a notice of the leaps which the 

 Mexican hare (Lcpus calliotis calliotis) and the sage hare 

 (Lcpus sylvaticus Nuttalli) make when put to their 

 utmost speed. The former makes bounds of twelve to 

 thirteen feet, and the latter of six to seven feet. The 

 distances were measured in a thin layer of newly-fallen 

 snow. It is to be noticed that Mr. Shufeldt uses the 

 trinomial nomenclature now common among American 

 zoologists. 



— ♦^>;^««5«f-. — 



THE GREEN COLOURING MATTER OF 



PLANTS. 



TN a former number we noticed some of the points of 

 ^ interest presented by the red colouring matter of 

 animals. What the red colouring matter is to the higher 

 animals the green colouring matter is in many respects 

 to the higher plants — equally prevalent or even more so, 

 equally necessary to the functional activity of the 

 organism, and hardly less complex in its chemical 

 and physiological relations. The function of the two 

 substances is not however identical. Haemoglobin is 

 solely of respiratory value, the green colouring matter 

 of plants is entirely nutritive in function. 



The green colour found in nearly all flowering plants 

 and very many others depends upon the presence of a 

 substance called Chlorophyll, which may be readily ex- 

 tracted by certain solvents, such as alcohol or benzine. 

 Water does not dissolve chlorophyll, but boiling in water 



renders the action of alcohol the more rapid, by freeing 

 the chlorophyll from the particles with which it is intimately 

 associated. A solution of chlorophyll is tinged with the 

 same green colour as the leaves. When examined by the 

 spectroscope, light which has traversed a chlorophyll 

 solution is found to have undergone change. Certain kinds 

 of rays in the violet and blue parts of the spectrum are fil- 

 tered out, and there is also a dark band between the lines B 

 and C, which indicates an important absorption of the 

 red rays. Another^optical characteristic of a chlorophyll 

 solution is its dichroism. When examined by trans- 

 mitted light it is ot 'a. beautiful green, but examined by 

 light falling upon it and with a black background, it has a 

 claret colour, perhaps due to the reflection of rays which 

 have been'absorbed and whose rate of vibration has un- 

 dergone change. 



The percentage composition, though not the chemical 

 constitution of chlorophyll, is known. It consists of the 

 four elements (carbon, hydrogen, oxygen, and nitrogen), 

 of which plants are almost entirely composed. Iron is 

 not believed to enter into the composition of chlorophyll, 

 but it is apparently as necessary to the green colour of 

 chlorophyll, as to the physiological activity of haemo- 

 globin. If a seedling be raised in an artificial soil from 

 which all compounds of iron have been scrupulously ex- 

 cluded, it has a blanched appearance, but if a solution 

 of some salt of iron be then painted over one of the leaves, 

 the green tint quickly appears wherever the brush has 

 passed. 



In the living plant chlorophyll is rapidly used up and re- 

 generated. This is shown by the blanching of a green plant 

 kept in the dark for a few days, and by the speedy re- 

 storation of the green colour when light is readmitted. 

 The blanched plant is not quite colourless, but yellow ; 

 it contains a yellow substance, Etiolin, which is nearly 

 allied to chlorophyll andjpossesses in'ssme degree the same 

 physiological properties. Other colouring matters are 

 common in leaves and flowers. There is, for example, a 

 red colouring matter (Erythrophyll), which is soluble in 

 water, and a yellow colouring matter (Xanthophyll), very 

 similar to chlorophyll, with which it is mixed in most 

 green leaves. Xanthophyll occurs nearly pure in bright 

 yellow flowers. 



The practical importance of chlorophyll lies in its 

 power of decomposing carbonic acid. The gas is ab- 

 sorbed by leaves, and wherever it comes in contact with 

 chlorophyll it is broken up, provided that the leaves are 

 illuminated with bright sunlight, or at least daylight. The 

 carbon is appropriated by the plant, and goes to form 

 starch and other useful substances, while the oxygen is 

 exhaled. This was proved so long ago as 1772 by 

 Priestley, who showed that plants of mint, spinach, and 

 balm rendered air which had become loul by respira- 

 tion again fit for breathing and capable of supporting a 

 flame. We now know that plants produce in sunlight 

 a gas capable of being identified with oxygen, that the form- 

 ation of oxygen by plants does not take place except in 

 sunlight, or some light of similar character, that an in- 

 creased supply of carbonic acid increases the yield of 

 oxygen, and that the absorption of carbonic acid produces 

 an increase of weight in the plant. By a modern micro- 

 scope it is easy to see the starch-granules newly formed 

 within chlorophyll bodies exposed for a few hours to 

 light, and which previously contained none. 



An impressive experiment, which may be made by 

 anybody, illustrates the formation of starch within a 

 green leaf. Take a broad leaf, «.^., of primrose, blanch 



