CHAPTER n. 



THE TISSUES OF PLANTS. 



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

 with any others; some which are at first separate afterward 

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

 are united to each other from the beginning of their exist- 

 ence into what are called tissues. 



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

 blage 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. In the lower plants the cells are all alike, or so nearly 

 so that they constitute but one kind of tissue. As we 

 ascend from these simple forms the cells begin to show 

 differences, some being especially developed for one pur- 

 pose, and some for another; and these differences become 

 more numerous and more sharply marked as we ppproach 

 the higher plants. This at last gives us many kinds of 

 tissues, which may be distinguished from each other by 

 characters of greater or less importance. However, they 

 may all be brought within seven general kinds, each kind 

 showing many varieties. 



36. Soft Tissue {Parenchyma). — This is the most abun- 

 dant tissue in the vegetable kingdom; it is at once the 



