Development of Dumontia filiformis. II. Development of Sexual Plants and General Discussion of Results

Abstract

Dumontia filiformis, during May, June, and the first half of July, grows in abundance in the tide pools and on the bed rock at South Harpswell, Maine. This alga became established on the coast at South Harpswell between 1905 and 1913. Antheridial, cystocarpic, and tetrasporic plants may have essentially identical size and vegetative structure. The average size of the antheridial plants is a little less than that of the other plants. Cystocarpic and tetrasporic plants are found growing together on the same rock and in the same tide pools. Female plants which bear mature cystocarps are easily recognized by the protrusions which these form in the wall of the thallus. The type of branching varies considerably. All male and female plants collected were branched. Tetrasporic plants, simple and branched, were found. The maximum number of branches observed on any individual plant was 30. The color of the plants varies from dark red to pale reddish yellow. Male plants bearing mature spermatia are present in the ea...