The vegetative and inflorescence apices of Myosotis laxa and Mertensia virginica have been compared and contrasted in order to determine how helicoid and scorpioid cymes differ in development. The apices have been interpreted on the basis of the tunica-corpus theory, since no clear histogenic layers could be determined for these species. The stem apex enlarges and broadens at the onset of flowering, and apical dominance is lost. The number of tunica layers is reduced in both cases, and the enlargement of the apex is found to be due to more, not larger cells. The helicoid cyme of Myosotis laxa results from a continuous renewal of meristematic activity on the same side of the apex. The scorpioid cyme of Mertensia virginica develops in a stepwise fashion as a result of renewed meristematic activity at ninety degrees from the previous point of growth. Both are sympodial axes.
Proceedings of the Iowa Academy of Science
©1960 Iowa Academy of Science, Inc.
Prior, Paul V.
"Development of the Helicoid andScorpioid Cymes in Myosotis laxa Lehm. and Mertensia virginica L.,"
Proceedings of the Iowa Academy of Science, 67(1), 76-81.
Available at: https://scholarworks.uni.edu/pias/vol67/iss1/11