STAGES IN PLANT EVOLUTION 



49 



The higher plants of to-day all consist of very large 

 numbers of cells forming tissues of different kinds, 

 each of which is specialized more or less, some very 



Fig. ig. — A, Details of Part of the Tissues in a Stem of a Flowering Plant. 

 E, Diagram of the Whole Arrangement of Cross Section of a Stem : e. Outer 

 protecting skin ; g, green cells ; s, thick-walled strengthening cells ; p, general 

 ground tissue cells, v, Groups of special conducting tissues: x, vessels for 

 water carriage ; p x, first formed of the water vessels ; c, growing cells to add 

 to the tissues; b, food-conducting cells; ss, strengthening cells. 



elaborately, for the performance of certain functions of 

 importance for the plant body as a whole. With the 

 increase in the number of cells forming the solid plant 

 body, the number of those living wholly cut off from the 



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