l62 THE STORY OF THE PLANTS. 



Now, leaves and flowers are, so to speak, the units 

 of the plant-colony, while stem and branches are 

 the community as a whole and the mode of its 

 organisation. You must know something about 

 the component parts before you can get to under- 

 stand the whole built up of them ; you must have 

 seen the individual citizens themselves before you 

 can comprehend the city or nation composed by 

 their union. 



The stem, then, is the part of the plant-colony 

 which does not consist of individual leaves, either 

 digestive or floral, but which binds them all to- 

 gether, raises them visibly to the air, and supplies 

 them with water, nitrogenous matter, and the re- 

 sults of previous assimilation elsewhere. The 

 stem' and branches are common property, as it 

 were ; they belong to the community : they repre- 

 sent the scaffolding, the framework, the canals, 

 the roads, the streets, the sewers, of the com- 

 pound plant-colony. 



How did stems begin to exist at all ? The 

 most probable answer to that question we owe, 

 not to any professional botanist, but to our great 

 philosopher, Mr. Herbert Spencer. 



The simplest and earliest plants, we saw, were 

 mere small floating cells, endowed with active 

 chlorophyll. Next in the upward order of evolu- 

 tion came rows of such cells, arranged in long 

 lines, like hairs or threads, or like pearls in a neck- 

 lace, as in the green ooze of ponds and lakelets. 

 Above these simple plants, again, come flat ex- 

 panded collections of cells, as in the fronds of 

 seaweeds. Now, all these kinds of plant are stem- 

 less. But suppose in such a plant as the last, one 

 frond or leaf took to growing out of the middle 

 of another, as it actually does in many instances, 



