The reproductive morphology of Dumontia incrassata (O. F. Müller) Lamouroux

The reproductive morphology of Dumontia incrassata (O. F. Müller) Lamouroux is described from New Hampshire, U.S.A. populations. Mature carpogonial and auxiliary branches are usually 5 and 6 celled, respectively, but both may range from 4 to 9 cells. Auxiliary branches are more numerous than carpogonial branches; however, the ratio of carpogonial to auxiliary branches increases towards the apex of the frond. A linear relationship exists between the position of the generative auxiliary cell and the number of cells in the auxiliary branches. In most cases the third cell from the top of the auxiliary branch becomes the generative auxiliary cell. The probabilities for different positions of the generative auxiliary cells are summarized. During spermatangial development, four mother cells are initially produced per cortical cell initial; subsequently, successive spermatangia are cut off obliquely and on opposite sides of each mother cell. Monoecious asexual plants of D. incrassata are described, as well as an irregular tetraspore development

Reproductive ecology of four subtidal red algae

The reproduction and stature of the red algae Callophyllis cristata (C. Ag.) Kuetz., Membranoptera alata (Huds.) Stackh., Phycodrys rubens (Huds.) Batt., and Ptilota serrata Kuetz. were recorded from subtidal populations at Appledore Island, Maine, U.S.A., with respect to time and depth. Only Membranoptera alata exhibited a conspicuous seasonal fluctuation of reproduction. A vertical gradient of reproduction was evident, with reduced levels of reproduction in shallow populations of Phycodrys rubens and Ptilota serrata, as well as deep populations of Phycodrys rubens, Membranoptera alata and Callophyllis cristata. Differential stratification of the reproductive phases of Ptilota serrata occurred with higher frequencies of tetrasporic plants in deep populations and of cystocarpic plants in shallow populations. In contrast, the haploid and diploid plants of the other three species showed similar distributional patterns. Membranoptera alata, Phycodrys rubens, and Callophyllis cristata showed a conspicuous decrease in stature during maximum reproduction