326 COMPOSITE ORGANS. CHAP. II. 



cending the stem directly, but winding more or less 

 around the axis of the plant. Du Hamel describes 

 it by saying that one or more of the fibres, originally 

 composing a bundle, quits it, and diverges towards 

 another bundle which it joins, but from which it 

 again separates to join the bundles it had originally 

 quitted ; or it unites itself to other diverging fibres 

 which it meets on the way, and so forms a new 

 bundle. But the intersections of the fibres do not 

 always take place in the same way in all plants, so 

 that the net-work peculiar to one species is often very 

 different from that of another. This may be seen by 

 comparing together the net-work of the barks of the 

 Oak and Elm, or of almost any other plants of dif- 

 ferent genera. 



Aggregate As the layers recede from the circumference, the 

 aspect. net-work which they form is finer, though still very 

 irregular, and their texture more compact. But 

 although the net-work is still irregular, yet the 

 meshes of the different layers often correspond, 

 forming an aperture that extends as far as the meshes 

 coincide, but diminishing in size as it penetrates 

 towards the centre, owing to the decreasing size of 

 the meshes, and forming, according to the illustra- 

 tion of Du Hamel, a pyramid, of which the exterior 

 mesh is the base. In the trunk of aged trees, such 

 as the Oak and Elm, the apertures thus formed 

 widen into large gaps and chinks, exhibiting still in 

 their distribution the rough traces of the net-work 



o 



of the original layer, now laid bare by the decay of 

 the epidermis and cellular integument. But in the 





