162 HISTOLOGY OF MEDICINAL PLANTS 
In the rhizome of calamus and other aquatic plants the 
intercellular spaces are very large. The cells of these plants 
are arranged in the form of branching chains of cells which thus 
provide for large intercellular spaces.. 
The cells of the middle layer of flower petals, like the meso- 
phyll of leaves, is loosely arranged owing to the peculiar branch- 
ing form of the cells. 
Seeds and fruits contain, as a rule, few or no intercellular 
spaces. 
