A thin section through a Begonia stem will show more rounded crystals, known as druses . Compared to most animals, vascular plants are quite simple in structure. The leaves plus the shoots make up the shoot system , while the roots collectively compose the root system . The arrangement of structures in the shoot system is very stereotyped, and hardly varies despite the great diversity in appearance and growth form of vascular plants. Shoots are constructed in modular fashion, with the basic module being composed of a leaf and a length of stem.
Buds are capable of growing into branches.
Branches may consist of vegetative or reproductive structures. Root systems also have a modular structure, although it is both simpler and less obvious than that of the shoot system. The basic module is a branch root . As the above suggests, modules have limited capabilities for producing other types of modules. Ordinarily, shoot modules are produced by branching from existing shoot modules, and root modules are produced as branches from existing roots.