VI] CELL-TISSUES 69 



parallel to the longitudinal axis of stems, roots, leaves, 

 fruits, tendrils, &c. two further general conclusions are 

 forced upon us. 



In the first place we discover that different kinds of 

 cells, in the sense referred to above, occur in one and the 

 same organ, as well as in different organs of the plant ; 

 and, secondly, that the various cells show more or less 

 definite grouping or arrangement with reference to the 

 centre or axis and the planes cutting this in the section. 

 In many cases, in fact, these groupings result in the 

 formation of beautifully symmetrical patterns. 



These sections also teach us still more clearly that the 

 cells are closed box-like chambers, of various shapes and 

 sizes, with walls differing in thickness and in other 

 respects, and enclosing very different cell-contents in the 

 different cases. 



The groups of cells which stand out on such sections are 

 called tissues, owing to the suggestion on the part of earlier 

 observers that some of the groups are woven into and 

 between others. The original idea was a mistaken one, 

 but the name has persisted, and will be used with a 

 totally different connotation, implying, as we shall see, 

 little beyond the truth that a tissue is a co-ordinated 

 group of cells more or less similar in behaviour and 

 appearance, and differing in these respects from other 

 groups (or tissues) which have their own peculiarities. 

 To some of these matters I shall return: meanwhile it 

 is necessary to examine a few further peculiarities con- 

 cerning the cell-structure of plants. 



Even the resistance which the razor meets with as it 

 passes through the plant-organ convinces us that the net- 

 work of cell- walls is more solid and continuous in some 

 cases than in others; and the microscope shows that while 

 in some cases the cell- walls are quite continuous, in others 



