230 Phytotomy founded [BOOK n. 



improved instrument ; as an adherent of the inductive method 

 he desired to aid in perfecting the perceptions of sense which 

 are the foundation of all human knowledge ; with this feeling 

 he submitted all sorts of objects to his glass, that it might be 

 known how much the unassisted eye fails to perceive. He 

 made what he saw texts for discussions on a multiplicity of 

 questions of the day. The book therefore was not devoted to 

 phytotomy ; the structure of the substance of plants is noticed 

 in the same incidental manner as the discovery of parasitic 

 fungi on leaves, or other similar matters. And what Hooke 

 saw of the structure of plants was not much, but it was new, 

 and on the whole fairly judged. It appears that he discovered 

 the cellular structure in plants by examining charcoal with his 

 glass, and that he then tried cork and other tissues. He says 

 that a thin section of cork on a black ground (by direct light 

 therefore) looks like honey-comb ; he distinguishes between 

 the hollow spaces (pores) and the dividing walls, and to the 

 former he gives the name which they yet bear ; he calls them 

 cells. The arrangement of the cork-cells in rows misleads 

 him into taking them for divisions of elongated hollow spaces, 

 separated by diaphragms. These, he says, are the first micro- 

 scopic pores which he or any one else had ever seen, and he 

 regards the cell-spaces of plants as examples of the porousness 

 of matter, as do the text-books of physics up to modern times. 

 Hooke employed his discovery especially to explain the 

 physical qualities of cork ; he estimates the number of pores 

 in a cubic inch at about twelve hundred millions. He draws 

 another botanical conclusion ; he gathers from the structure 

 of the cork that it must be an outgrowth from the bark of a 

 tree, and appeals to the statements of one Johnston in proof 

 of this hypothesis. The fact, that cork is the bark of a tree, was 

 therefore not yet known to all educated people in England. 

 Hooke afterwards says that this kind of texture is not confined 

 to cork ; for as he examined the pith of elder and other trees 

 with his microscope and the pulp of hollow stemSj such as 



