28 A TEXT-BOOK OF BOTANY 



thesis, and this process is carried on by the green tissue of 

 the globular, cylindrical, or flattened stems (Fig. 25). 



FIG. 25. A globular cactus, '.vith ribbed stem bearing spines and no foliage leaves. 



(6) The rosette-habit ( 12) is a very common method of 

 protection used by small plants growing in exposed situa- 

 tions, as bare rocks and sandy ground. The clustered 

 leaves, flat upon the ground or nearly so, and more or less 

 overlapping, form a very effective arrangement for resisting 

 intense light or drought (Figs. 6 and 7). 



