LEAVES 



The leaves of mosses vary in size, shape, arrange- 

 ment, position, and color, and it is necessary to train 

 the eye to notice these variations in order to recognize 

 the generic characteristics. 



Care must be taken not to mistake branches for 

 leaves, when the leaves are very small and the branches 

 are more conspicuous. 



Mosses branch much like other plants and the leaves 

 are much more numerous than the branches, some- 

 times thickly covering both the stem and the branches. 

 When the leaves are very small and closely folded, the 

 branches look cylindrical, but if the plants are held to 

 the light, at least the tips of the leaves can usually be 

 seen sticking out around the branches. 



Unlike the leaves of other plants, the leaves of 

 mosses nearly always consist of only a single layer of 

 cells, except where the midrib occurs or at the margin 

 of the leaf when it is thickened. This simple structure 

 makes the leaves dry readily and also absorb moisture 

 readily, and adds a special interest to the study of 

 mosses, as dried specimens can be easily restored to 

 fresh conditions by being placed in water for a few 

 minutes. This has been tried with plants that had re- 

 mained dry for over one hundred years, and it was 

 found that the leaves still expanded quickly. In an- 



