CHAPTER III 
GROUPS OF TISSUES, OR TISSUE SYSTEMS 
HISTOLOGY 
55. In the lower plants, where all cells are essentially 
alike and no distinction of tissues can be made, we often 
find that growth takes place in all parts of the plant, al- 
most every cell being capable of growth and division at 
any age. In many plants, however, in which the differ- 
entiation into various kinds of tissues is still almost lack- 
ing, we find that growth is more or less limited to certain 
regions of the plant. In those plants where the tissue 
differentiation is strongly marked, we find that the 
formation of new parts, as well as growth, is localized 
in groups of meristem cells at the apices of stems and 
roots (and also in many plants at the nodes), the older 
cells of these groups gradually changing into the more 
permanent tissues of the plant. 
56. In many seaweeds and fungi, where the plant 
body consists of separate or adjacent rows of cells, the 
terminal cell of each row elongates and divides by a 
cross partition and perhaps division occurs in one or two 
cells behind it. Except for the formation of branches, 
longitudinal divisions may be lacking and the result is 
only the formation of rows of cells. 
57. In the plants which are not so markedly fila- 
mentous in structure the new tissue at the apex may arise 
by the division of a single apical cell. This division 
may be by horizontal partitions, the segments thus 
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