460 BOTANICAL GAZETTE [june 



considerably. All male and female plants collected were branched. 

 Tetrasporic plants, simple and branched, were found. The maxi- 

 mum 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 

 early part of April and two weeks later have almost completely 

 disappeared. Young female plants were found on April 12, and 

 these reach their maximum stage of development about the middle 

 of May. Tetrasporic plants are most abundant in the latter part 

 of June and have almost entirely disappeared by the first of August. 

 Dumontia at South Harpswell must persist through the winter in 

 the form of sporelings developed from the tetraspores. 



The vegetative structure is of a type occurring in many families 

 of the Florideae. The disk-shaped holdfast is composed of a single 

 layer of horizontal filaments, each cell of which produces a vertical 

 ascending branch. Certain of these branches elongate to form the 

 medullary hyphae of the tubular thallus. Each medullary hypha 

 has its own initial cell. Every cell of each medullary hypha 

 produces a radial branch. These radial branches, by repeated 

 dichotomous forking, form the subcortex and the cortex. Growth 

 is apical throughout the entire thallus. All the other vegetative 

 cells, except the trichomes, are uninucleate and contain one chroma- 

 tophore each. All the chromatin in the resting nucleus is in the 

 nucleolus. The chromatophore is a clathrate hollow ellipsoid, lying 

 just inside the cell wall. 



The tetraspores are imbedded in the wall of the thallus, and 

 are distributed evenly throughout practically the entire length 

 and circumference of the branches and main axis. Younger tetra- 

 sporangia are found toward the base of the plant. The larger 

 subcortical cells become modified to form the tetrasporangia. The 

 chromatophore becomes constricted at intervals, so that it appears 

 to consist of rows of small irregular plates. These bodies persist 

 through all stages of the tetrasporangium, and their number is 

 increased in the tetraspores. No spindle or spireme was seen. 

 The chromatin in some of the nuclei is in several small bodies, 

 but these do not resemble chromosomes. The first cleavage 

 furrow completely divides the tetrasporangium, is perpendicular 



