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CORRESPONDENCE. 



The difference between the Wood of Trees which have died, and that of 

 those which have been felled. 



To the Editor of the Naturalist. 



Dear Sir, — Your correspondent, the Rev. F. O.Morris, inquires : — Is there any 

 difference for purposes of use between the wood of trees which have died, and those 

 which have fallen under the axe ? On putting this question to a practical man, a 

 carpenter, he replied, that the wood of trees which have died is rough, and does not 

 "work up so well" as those felled by the axe ; the wood next the bark being roughest. 

 He was not aware that there was any difference in the duration and strength 

 of the timber, provided both were sound. This is the answer that might have 

 been expected from a previous knowledge of the functions of the wood of trees. 

 The wood of trees is distinguished by botanists into two kinds ; the central 

 wood deposited in previous years' growth and containing the peculiar secretion 

 of the tree, called duramen, or heart wood, and the external layers of wood, 

 deposited in the last years of the growth of the trees, and not yet filled with 

 the consolidating secretions, called alburnum, or sap-wood. The largest portion 

 of the nutritive sap of the tree ascends to the leaves through the alburnum, only 

 a small quantity being more or less diffused through the duramen. When a 

 tree dies, it generally arises from the stoppage or vitiation of the sap, and, con- 

 sequently, we find that the smaller branches, or those composed entirely of sap- 

 wood, suffer most, and are easily broken. As we approach nearer the stem the 

 branches become stronger in proportion to the duramen they contain, and the 

 wood of the trunk consisting chiefly, in timber trees, of duramen, appears to 

 suffer very little. The sap-wood, of course, would suffer more or less according 

 to its age, but the heart-wood, being almost entirely independent of the sap, 

 could not suffer from its suspension or vitiation. 



The Distinctions between Quercus pedunculata and Q. sessiliflora. 



Mr. Davis, in his interesting paper on the decrease of the Oak, in your 

 Naturalist of last month, has not alluded to a circumstance that has, probably, 

 had some influence in reducing the number of our Oak-forests. Perhaps you will 

 allow me to draw the attention of your readers to it. There are two species of 

 Oak indigenous in Britain, Quercus peduncidata and Quercus sessiliflora; the 

 former is known by its long flower-stalks, and short leaf-stalks ; the latter by its 

 short flower-stalks and longer leaf-stalks. Q. pedunculata is a slow-growing 

 tree, with bright green leaves. Q. sessiliflora is much more rapid in its growth, 



Fo. 12, Vol. II. 2t 



