CHAPTER II. 

 THE TISSUES OP PLANTS. 



33. Some plant-cells live alone, and are not connected 

 with any others; some which are at first separate after- 

 ward unite into a cell-colony. In most cases, however, 

 the cells are united to each other from the beginning of 

 their existence into what are called tissues. 



34. As understood in this book a plant-tissue is an 

 assemblage of similar cells which have been united with 

 each other from their beginning. The cells in a tissue 

 may be arranged in rows, surfaces, or masses : in the first 

 the growth has been by the fission of cells in one plane 

 only, in the second from fission in two planes, and in the 

 third from fission in three planes. 



35. Eudimentary Tissue (Meristem). — When the cells 

 are young their walls are thin and alike, but as they grow 

 older they change in shape, in the thickness and mark- 

 ings of their walls, as well as in their contents. Every 

 cell has its young state, its period of active growth, and 

 finally its condition of maturity. Tissues composed of 

 immature cells are thus much alike, but as they grow 

 older they are differentiated more and niore. "We may 

 thus distinguish between rudimentary and permanent tis- 

 sues, and since the latter constitute the bulk of the mature 



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