PLANT STUDIES 
one. Perhaps the most complete fitting together of leaves 
is found in certain ivies, where a regular layer of angular 
interlocking leaves is formed, the leaves fitting together like 
FIG. 18. A plant (Pellionia) with drooping stems, showing how the leaves are all 
brought to the lighted side and fitted together. 
the pieces of a mosaic. In fact such an arrangement is 
known as the mosaic arrangement, and involves such an 
amount of twisting, displacement, elongation of petioles, 
