© 1974 by The Society for Integrative and Comparative Biology
Cell Proliferation in the Terminal Regions of the Internodes and Stolons of the Colonial Hydroid Campanularia flexuosa
Department of Zoology, Indiana University Bloomington, Indiana 4740
Pattern formation and cell proliferation have been believed to have a causative relationship in the colonial hydroids. Here linear stolon growth was assumed to be dependent on polarized cell proliferation restricted to the extreme end of the stolon. The popularity of the concept that pattern formation was a result of restricted meristematic cell proliferation was based on a correspondence between the observed growth patterns and the concept. Nevertheless, there is little direct knowledge of cell proliferation in the stolons of hydroids.
The primary objective of this investigation was to determine the sites of cell proliferation in the terminal growth zones of the colonial hydroid Campanularia flexuosa in order to evaluate this concept. The results give evidence that cell proliferation is more or less uniformly distributed throughout the terminal stolon and the internodes of upright stems, and not restricted to the tips of the stolons and internodes as has been previously postulated.
Cell proliferation occurs in both the epidermis and gastrodermis of the stolon in a ratio of 3 to 2. The formation of a new upright is accompanied by increased cell proliferation localized at the site of initiation.
The uniform distribution of cell proliferation in the stolon supports the hypothesis that growth is via intercalary cell proliferation, which was proposed eailier on the basis of evidence obtained from the displacement of vital stained bands of tissue in the stolon.
Stolon growth via intercalary cell proliferation requires a reconsideration of the factors which control morphogenesis. Wolpert has pointed out the importance of determining the mitotic pattern in a developing system before an understanding of positional information within the system may be studied. Thus, information for greater insight into the study of positional information in a developing hydroid has been obtained.