418 



THE MICROSCOPE. 



arise from the terminal enlargement of each fibre being its free nucleolus ; 

 and he also assumed that the motile threads, or vibratory cilia, found 



fig. 199. 



1. Woody fibre from the root of the Elder, exhibiting small pores. 2. Woody fibre of 

 fossil wood, showing large pores. 3. A section of stem of Clematis, with pores. 

 At 4 the pores are highly magnified, to show the line which passes round them. 



5. A vertical section of a leaf of the India-rubber tree, exhibiting a central gland. 



6. Woody fibre, bordered with pores and spiral fibres. 7. Portions of fossil wood 

 taken from coal. 



on the spores of some alga3, &c., are of an analogous nature, each spore 

 being a nucleolus. 



In fig. 199, "No. 1, we have a modification of the cellular tissue, 

 with its sides marked by pits or dots, produced in consequence of the 

 cell contents being unequally deposited over the inside of the cell-wall 

 or membrane. The office of this peculiar tissue is said to be for the 

 purpose of conveying fluids with rapidity in the direction of the woody 

 tissues that surround it, or from the lower to the upper limbs : it is 

 commonly recognised as the porosity of wood. Common woody fibre 

 (Pluerenchyma) has its sides free from definite markings. In the 

 coniferous plants, the tubes are furnished with circular disks, shown 

 at No. 6, fig. 199. These disks are thought to be contrivances to 

 enable the tubules of the woody tissue to discharge their contents from 

 one to the other, or into the cellular spaces. Such as have aromatic 



