12 LETTER I. 



animals with wholesome food. The plant itself could 

 not grow without them ; or, if it grew, could not 

 bear fruit, but would totally perish as soon as it was 

 born. The business of the leaves is to suck out 

 of the stem the watery food which the roots had 

 sucked out of the soil, and the stem out of the roots ; 

 and having filled themselves with it, to expose it to 

 light and to air, to evaporate the superfluous part, 

 and having thus in a manner digested it, to discharge 

 it again back into the stem in the form of the peculiar 

 matter which it may be the property of the plant to 

 produce; such for instance as sugar in the Sugar 

 Cane, flour in the Potatoe, gum in the Cherry Tree, 

 a powerful medicinal substance in the Peruvian Bark 

 tree, and poison in the Ranunculus itself. In order 

 to enable the leaf to convey the watery food it sucks 

 out of the stem to all parts of its own surface, and to 

 return it back again, nature has furnished this little 

 organ with a most curious and complicated arrange- 

 ment of drains or conduits, consisting of excessively 

 minute water-pipes glued together and branching in 

 every direction ; these are what we call veins ; which 

 you see in the Ranunculus are all joined together in 

 the stalk of the leaf, but separate as soon as they enter 

 the leaf itself, when they first divide into a few large 

 arms, then subdivide into a number of smaller ones, 

 and again divide over and over again until at last they 

 form a net with meshes finer and more delicate than 

 the most exquisitely manufactured lace. If you could 

 examine the veins with a microscope you would find 

 them still more curious in their structure than I have 



