Vol. IX. No. 207 



THE AGRICULTUKAL NEWS. 



101 



the bud has made two flushes, and often it is not necessary 

 at all, since the raffia usualh' decays beneath the waxed cloth, 

 and the latter naturally expands with the growth of the 

 stock. When the bud has started into growth, the top of the 

 tree may be completely cut off and destroyed. The .stump 

 remaining above the bud may be cut off with a sloping cut 

 close to the bud, after the latter has made three or four 

 flushes. 



ADVANTAiiES oK THE METH0i>. It has been found that 

 buds can be set quite rapidly by this method. In the exper- 

 ience of the writer, live or six buds could be set, by this 

 means, to one by the patch bud method. Speed may be 

 increased also by the use of unskilled labour in the tying and 

 binding operations. The operator can set the bud and pass 

 on to the next without any danger of its getting out of place 

 before the helper, who immediately follows, ties it. 



Pfrhaps the most important advantage in this method of 

 budding lies in the fact that it may be used successfully when 

 the bud-wood is not in an active growing condition. The 

 most tedious part of patch budding is in removing the bud, 

 and frequently in doing so it will be broken. Further, it is 

 often impossible to get bud wood of a desired variety in 

 active condition when the stocks are ready to be operated 

 upon. 



The method may be applied most advantageously to 

 seedling trees in orchard form when they have become large 

 enough to be operated upon, when the buds .should be set 

 only a few inches above the ground. It may also be used in 

 top-working old trees to new varieties. 



WHY PLANTS ARE GREEN. 



An endeavour has been made recently by Professor 

 (Stiihl to account for the fact that the higher, as well as many 

 of the lower, plants are green. It is well known that the 

 green colour of such plants is due to the po.sse.ssion by them 

 of a colouring matter called chloroiihyll, and the object 

 of the enquiry has been to find out why this should possess 

 that colour rather than any other. Starting from the fact 

 that ordinary white light is composed of the primary colours — 

 red, orange, yellow, green, bhie, indigo and violet — that is 

 the colours of the spectrum, it is easy to understand that 

 chlorophyll owes its greenness to the fact that it ab.sorbs 

 much of the light at the red and blue ends of the spectrum, 

 and rejects the green. This absorption of the red and blue 

 rays can be simply demonstrated by allowing light of either 

 of those colours to fall on the green parts of a plant, when 

 they appear almost black. 



The light that is absorbed by a green jilant i.?, of course, 

 used as the source of energy by means of which it builds up 

 the more complex compound.s, required in its life-processes, 

 from simple ones. For this [juruose, the red and orange rays 

 are used chiefly. The work of Stahl and other investigators 

 shows that the energy from the blue end of the sjiectruni is 

 also employed in the same way. All these useful rays would 

 be absorbed equally well if the leaves were black or grey. 

 Why is it, then, that they are green? In other words, why is 

 it that the trouble is taken to exclude most of those rays from 

 the leaf that are not required to enable it to carry on its work? 



In order to assist in obtaining an answer to this 

 question, reference is made to the seaweeds. The red 

 seaweeds contain a red colouring matter which surrounds, 

 and gives rise to, the green colouring matter (chloro- 

 phyll) that is present in their cells. It may be proved 

 that they possess chlorophyll by placing them in hot 

 water, when they become green. A question immediatelj' 

 arises as to why such seaweeds possess a red, as well as a green, 



colouring matter. It is solved by referenca to the fact that 

 these plants usually live in deep water. The colour of water 

 is blue, that is to saj-, if white light passes through a suffi- 

 cient depth of it, only the blue rays will remain unabsorbed. 

 The result of this is to cause the light which reaches a plant 

 of red .seaweed, growing in its usual habitat, to contain 

 a very small proportion of the orange and red rays. These 

 are, luiwever, the very rays that are absorbed by the chloro- 

 phyll for the purpose of providing energy in order that food 

 may be manufactured for the uses of the plant, and the fact 

 of the small amount of these kinds of I'.aht makes it exped- 

 ient that means shall be provided by which the rays that are 

 present in greater proportion shall be utilizecj in this manu- 

 facture. This is where the use of the led pigment is found. 

 It absorbs some of the blue and green light, and thus 

 provides additional energy for the needs of the plant. Such 

 absorption is rendered possible by the fact that the colour of 

 this pigment (red) is complementary to that of the surround- 

 ing water (blue). 



The application of these facts has now to be made to 

 chlorophyll in plants which live under ordinary, atmospheric 

 conditions. Cldorophyll actually con.sists of two pigments — 

 a blue-green one, which absorJas si)ecial!y red and orange 

 rajs, and a yellow-orange pigment, which acts in the same 

 ■way toward blue rays. The light which reaches a plant is of 

 two kinds : that which falls u;:on it directly from the sun, 

 and that which only reaches it after reflection from surround- 

 ing bodies — diffused light. In the foruier, the red and 

 orange rays are present in the greatest proportion; in 

 difl'used light, they are not found tf) the same extent, and 

 there is more blue light. But from what has just been said, 

 these are absorbed by the blue-green and the orange-red 

 pigment, re.spectively. Thus the presence of the first-named 

 pigment is to enable the plant to take advantage of direct 

 sunlight, and of the orange red pigment to enable it to make 

 the best u.se of ditt'used sunlight. 



The colour of leaves, then, is not black or grey, even 

 though in this case the}' would absorb the largest amount of 

 energy for the purpose that they have to fulfil in the 

 economy of the plant. The reason is that, with such colours, 

 the amount of light absorbed would be sufliciently large to 

 cause injury to the protoplasm that they contain. They are 

 green because they contain pigments that enable the right 

 kinds and quantity of light to be absorbed, whether this is 

 received directly from the sun or after reflection from surround- 

 ing objects. 



Yield of Copra from Cocoa-nuts. 



An account of trials that were carried out at the Expeii- 

 ment Station, Peradenij-a, Ceylon, in order to find out what 

 percentage of copra could be obtained from cocoa-nuts is 

 given in the Tropiral Af/riridturist for .January 1910. The 

 nuts employed were generally small, and, for the purpose of 

 the investigation, 10,000 of them were taken. The results 

 of the experiments were as follows: — 



B). per cent. 



Weight of nuts ... l,284-.5 (1000) 



., water in nuts ... 16.3'.5 12'7 



shells ... 3160 28-6 



,, kernels ... 7-o3'5 58'7 



From the kernels, the weight of dry copra obtained was 

 337-5 H).; that is to say, the kernels yielded 41-8 per cent, of 

 their %veight in cojira. In the same way, the weight of the 

 dry copra was 26'3 per cent, of that of the nuts. 



This is expressed difterently by saying that 1 ton of 

 cocoa-nuts may be expected to yield 1,31.5 lb. of kernels, 

 from which o89 B). of copra will be obtained. 



