50 PROSERPINA. 



are green when they do not grow in or near smoky 

 towns; and not by any means to rest content with 

 the fact that very soon there will not be a green 

 leaf in England, but only greenish-black ones. And 

 thereon resolve that you will yourself endeavour to 

 promote the growing of the green wood, rather than 

 of the black. 



9. Looking at the back of your laurel-leaves, you 

 see how the central rib or spine of each, and the 

 lateral branchings, strengthen and carry it. I find 

 much confused use, in botanical works, of the 

 words Vein and Rib. For, indeed, there are veins 

 in the ribs of leaves, as marrow in bones ; and 

 the projecting bars often gradually depress them- 

 selves into a transparent net of rivers. But the 

 mechanical force of the framework in carrying the 

 leaf-tissue is the point first to be noticed ; it is 

 that which admits, regulates, or restrains the visible 

 motions of the leaf; while the system of circula- 

 tion can only be studied through the microscope. 

 But the ribbed leaf bears itself to the wind, as the 

 webbed foot of a bird does to the water, and needs 

 the same kind, though not the same strength, of 

 support ; and its ribs always are partly therefore 

 constituted of strong woody substance, which is 

 knit out of the tissue ; and you can extricate this 

 skeleton framework, and keep it, after the leaf- tissue 



