CHAPTER IX. 



CO-OPERATION. 



It was not in altogether a figurative sense that 

 we regarded leaves as vegetable units, the equivalents 

 of zooids in such polypidoms as a Sea -fir. Every 

 plant, shrub, or tree may be looked upon as a colony 

 of such units ; a co-operative society on a varying 

 scale, ranging from individuals possessed of merely 

 a thallus, like Seaweeds, Liverworts, etc., to herb- 

 aceous plants with not more than half a dozen real 

 leaves, and upwards to the lordly Oak and gigantic 

 Euphorbias with their myriads. Vegetable society, 

 like human, is therefore collected into villages, small 

 towns, and populous cities. The leaves of a plant 

 share in the mutual benefit of its life. A tree is a 

 nation, with its units of leaf-population coming and 

 going year after year. It is subject to the same 

 laws of rise, decline, and ultimate fall, which history 

 shows has characterised the national life of many 

 countries. Its defensive thorns, prickles, spines, 

 poisons, etc., are to it what such defensive resources 



