. The algae. Algae. Fig. 146 Plumaria elegans. A, plant ( x f). B, antheridial ramuli ( X 180). C, paraspores ( x 213). D, tetrasporic ramuli ( x 126). (A, original; B, after Drew; C, D, after Suneson.) The antheridia are borne on special branches, whilst the four- celled carpogonial branch develops from the subterminal cell of an ordinary branch. In northern waters P. elegans never bears sex organs and only plants with paraspores are to be found, whilst in southern waters the sexual (n = 3i) and tetrasporic plants (n = 62) are predominant. Recent investigation has shown that in this species w
. The algae. Algae. Fig. 146 Plumaria elegans. A, plant ( x f). B, antheridial ramuli ( X 180). C, paraspores ( x 213). D, tetrasporic ramuli ( x 126). (A, original; B, after Drew; C, D, after Suneson.) The antheridia are borne on special branches, whilst the four- celled carpogonial branch develops from the subterminal cell of an ordinary branch. In northern waters P. elegans never bears sex organs and only plants with paraspores are to be found, whilst in southern waters the sexual (n = 3i) and tetrasporic plants (n = 62) are predominant. Recent investigation has shown that in this species we are concerned with a triploid race (n=93) in the northern waters which reproduces by means of paraspores. There is apparently no relation between the triploid plants and the other two races, and, furthermore, the triploid has the wider distribution because it is able to penetrate into the colder waters of the north. Tetraspores are to be found on the triploid plants but their chromosomal com- plement and fate are not known. Although both tetra- and para- sporangia arise from a single cell it is doubtful if the two structures are homologous. The reasons for this are first, the difference in chromosomal complement, secondly, the absence of any apparent relationship with the haploid and diploid plants, and thirdly, differ- ences in the mode of development of the para- and tetrasporangia. This is the first cytological record of triploid plants in the algae. Plumaria elegans is therefore tetraphasic morphologically and triphasic cytologically. It is possible that other algae may exhibit the same phenomenon. 257. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Chapman, V. J. (Valentine Jackson), 1910-. London, Macmillan; New York, St. Martin's Press
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