6o6 The Jotirnal of Forestry. 



bud, the "plumule" or "gemmule" of the embryo, and during its 

 growth is terminated by a bud at every growing point, only ceasing 

 to be so when it produces a flower at the end of the shoot, or loses it 

 from injury or disease. The way in which buds develop determines 

 the shape of the tree. Buds develop into branches ; but in a forest 

 where the trees are thick the lower branchlets die from want of light, 

 so that the tree appears to have been always destitute of lower 

 branches. These, however, leave evidence of their former presence in 

 the knots in the wood. 



It may be said generally that every plant-cell is capable of independ- 

 ent growth, so it is hardly an anomaly that stems or branches 

 mechanically injured, as in felling or pollarding, have the power of 

 throwing out " adventitious " buds from their stumps. The stem of 

 the lower groups of plants and that of the higher when in its earliest 

 stage consists merely of cellular tissue ; but in the latter " vascular 

 tissue," made up of vessels or ducts formed by the obliteration of the 

 horizontal partitions between cells, and of long lignified wood-cells, 

 soon originates. These ducts and wood-cells are grouped in bundles 

 and in all " dicotyledons " these are arranged in rings, being formed 

 just within the bark, which at first is merely the single layer of 

 superfical cells or " epidermis," The cellular tissue of the interior of 

 the stem persists, when surrounded by the rings of woody bundles, as 

 the "pith," and extends between the constituent bundles of these 

 rings as the "pith-rays," " medullary rays," " silver grain " or " felt." 

 These rays are well seen in beech, oak, and maple, less distinctly in 

 lime, yew, and chestnut, and are not traceable in fir wood. Though 

 the pith, at first full of sap and active in growth, is often broken up in 

 herbaceous plants, leaving a hollow stem, in trees it remains as a mere 

 point or line in the centre of the stem. 



The cellular tissue between the epidermis and the young woody 

 bundles remains in a growing condition, and is called the " cambium." 

 In its outer portion annual layers of long, tough cells are formed, 

 which are known as " bast." These render the bark tough, and enable 

 it to be stripped off. These annual layers are sometimes separated 

 by cellular tissue, and may thus be divided, as in Russia matting, the 

 lace bark, and Cuba bast, the products of the lime {Tilia Euro2')cea), 

 Lagctta Untearia, and Paritiuui datum. Most other textile materials, 

 except cotton, are bast. 



The epidermis of young stems is replaced by the cork layer, which 

 gives their external appearance to different trees. In the birch it is 

 formed of alternate layers of large and small cells, and so splits off 

 and rolls up. In the plane it is thrown off in plates ; whilst in the 

 maple, elm, and oak, especially the cork oak (Quercus suher), it 

 receives regular additions from the inside, and, not separating, becomes 



