l(^Q ON THE DIFFEREJiT SORTS OF WOOD. 



to increase in wood, as long as the hardened parts about it 

 will permit, adding one little row of wood each year, but 

 this soon ceases. It is perfectly detached from the rest of 

 the plant; and afterward pushed towards the exterior by the 

 growing part of the plant, while the sap continjes to cir- 

 Bnllsinthe culate round it and within it. The constant pressure these 

 *^ ' balls receive makes them grow to an inconceivable hardness ; 



and, when taken out, I have found them from twelve inches to 

 a quarter of an inch in diameter, and so rea^ularly formed, 

 (see fig. 5) that had I not taken them myself from the tree, 

 I should liave been persuaded they were just turned in a 

 lathe. Some are round, but with a single wood vessel at- 

 tached to them ; some formed like a spinning top. Here 

 is an old tree, that has formerly been in a hedge-row, that 

 has three balls about twelve inches in diameter. Carpenters, 

 when they find them, use them as heads, cogs of wheels, or 

 for any purpose that requires extreme hardness. 

 The forming The next peculiarity of the wood 1 have never yet tho- 

 ofhungry roughly explained is the exact reverse, in effsct, of the 

 ball; and the cause of both can be described by a drawing: 

 it is what the French call hungry wood, it proceeds from 

 some accident, a severe season, lightning, or injury the 

 tree has received. Some wood is much more liable to it 

 than others. It is a formation that is quickly finished, but 

 that stops many of the sap vessels, so that the wood is soft 

 and poor. I have often found a piece in the middle of 

 beautiful perfect wood so diseased. Hungry branches are 

 often seen shooting from the roots of trees. The rose, the 

 viburnum, the barberry, and many shrubs as well as trees, 

 are subject to this defect. Among trees the plane, the ash, 

 and the lime in particular are most liable to it; it is to be 

 known by its difference of appearance. To show it I shall 

 draw a piece of solid good oak, and a piece so affected, having 

 these specimens now in my possession. Fig. 3 is the healthy 

 piece, fig. 4 the diseased oak : cc are the sap vessels, dd are 

 the intermediate parts of both. When young, the wood is 

 wider between the sap vessels, but not near so far apart as 

 the diseased wood, which never appears to contract, as all 

 No wood with- perfect wood does. It is this effect, that has made many 

 out sap. physiologists think, that the sap vessels dried up, when the 



wood 



