The Coffee Board of Kenya Monthly Bulletin March 1944

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We have "now dealt with the fundamental processes which occur in plants;the absorption of carbon dioxide, which is converted into carbohydrates by the energy from the sun's rays, respiration,by which the energy is liberated for other processes, and the absorption of water and of various mineral substances.The channels by which water is absorbed and distributed throughout the plant have been described, but we have not yet considered how the carbohydrates and the minerals are moved from where they are formed or absorbed to parts of the plant where they are needed or where they are to be stored.Water moves mainly in the wood, which in older stems forms a more or less thick ring, but which in the young shoots consists of a' number of separate bundles of very much elongated cells.These bundles are accompanied on their outer surfaces by a group of elongated cells of another type,which are thin walled.In contrast to the cells of the wood, which die at an early age,they contain much living protoplasm.These cells form the tissue known as phloem,and in older stems it forms a complete but relatively thin ring around the wood.They appear to be the main channels through which carbohydrates move.Some few investigators claim that these substances move mainly in the wood... but although this may possibly occur to a certain extent,there seems little doubt that the phloem is the main channel.
Bulletin, IX (No 99), pp. 25-36