There are remarkable convergences in form that can be found in unrelated plant groups. For instance, the branching pattern of the green alga, Chara, is very similar to that of the Norfolk Island pine. This similarity in the branching pattern is due to a similarity in developmental processes.

      Why do some plants develop in the same manner, while others develop in entirely different manners? Differences in the developmental events that lead to variation in plant form may be evolutionary responses that occur to environmental changes over time.

      Consider a single spherical cell. A single spherical cell has the potential to develop into a number of different forms that may be adapted to different environments. A single spherical cell may divide to form a spherical colony (e.g. Volvox) adapted to roll around in an aquatic environment. A single cell may divide and grow to form an upright (orthotropic) cylinder adapted to grow quickly above competitors in order to take advantage of limited sunlight. Or a single cell may form a flat plane that provides a large surface area for photosynthesis.

      There are coenocytic organisms that are composed of a single cell with multiple nuclei. These cells may take on a variety of forms, therefore, cell division is not necessary for shape differentiation for all organisms.