Life History of Corallina Officinalis var. Mediterranea

The male and female plants of Corallina possess twenty-four chromosomes, while the tetrasporic plants have forty-eight chromosomes. 2. During the formation of tetraspores the forty-eight chromosomes become reduced to twenty-four. The tetraspores on germination show twenty-four chromosomes, and since twenty-four chromosomes appear in the vegetative mitoses of the sexual plants, the inference is that the latter arise from tetraspores. 3. The nuclei of the reproductive cells (spermatia and carpogonia) of the sexual plants possess twenty-four chromosomes. The sporophytic or fusion nucleus, as a result of fertilization, has forty-eight chromosomes. The sporophytic nuclei give rise by division to the carpospores, which also possess forty-eight chromosomes. The carpospores on germination show forty-eight chromosomes, and since forty-eight chromosomes appear in the vegetative mitoses of the tetrasporic plants, it is inferred that the tetrasporic plants originate from carpospores. 4. The male and female plants are gametophytic, while the tetrasporic plants are sporophytic. The sporophytic generation begins with the formation of the sporophytic or fusion nuclei, extends through the formation of the cystocarp and carpospores, and finally terminates with the formation of tetraspores on the tetrasporic plant. With the formation of the tetraspores, the gametophytic generation commences. 5. Thus Corallina is another clear example of the alternation of a sexual plant (gametophyte) with a tetrasporic plant (sporophyte), the cystocarp occurring as an early phase of the sporophytic generation.