HOWE: DIMORPHISM IN GALAXAURA 193 



evidence associating the groups "Vepreculae" and "Brachycladia" 

 seems particularly convincing. The name "Vepreculae" was given 

 by Kjellman to a "section" of the genus in 1900. "Brachycladia" 

 was proposed by Sonder as a separate genus in 1853 and is recognized 

 as an independent genus by De-Toni in his "Sylloge Algarum," though 

 by Kjellman it is properly considered to represent a section of Galax- 

 aura. In the "Brachycladia" group, the cortex is essentially fila- 

 mentous, as to its two outer layers at least (text-figure i), and the 

 cells separate easily after decalcification, though forming a more or 

 less coherent epidermis in the natural calcified condition. The outer- 

 most or superficial cells are usually oval or ellipsoid and obtuse or 

 apiculate. In plants of the section "Vepreculae," the cortex (text- 

 figure 2) may be said to be parenchymatous or pseudoparenchyma- 

 tous rather than filamentous. The epidermis here consists of cells 

 that are firmly united both before and after decalcification and these 

 cells have their longest axis parallel to the general surface instead of 

 at right angles to it. In some parts of the thallus, especially at the 

 edges of the flattened branches, the surface shows few or numerous, 

 scattered or crowded, blunt or apiculate, papilla-like cells, which are 

 probably homologous with the outermost or epidermal cells in the 

 "Brachycladia" section, though they do not here form the epidermis, 

 the firmly united epidermal cells of the "Vepreculae" section being 

 probably homologous with the%widely spaced subepidermal stalk-cells 

 of the "Brachycladia" section. Now, an examination of a wide 

 series of plants of the "Brachycladia" structure from the West Indies, 

 as well as an examination of the type material of nearly all of the 

 species from various parts of the world referred to this section by 

 Kjellman, indicates that whenever reproductive organs are found, 

 the plants of this group are always tetrasporic, and, in the same way, 

 plants showing the "Vepreculae" structure are always antheridial or 

 cystocarpic. Moreover, in the West Indies, at least, the writer's 

 personal experience in collecting shows that plants of these two types 

 of cortex-structure often occur together and that they show the same 

 or parallel variations in external habit. They resemble each other 

 very much in size and habit (plate III; plate IV, figure i), but may 

 usually be distinguished under a hand-lens, if not at sight, by differ- 

 ences in the texture of the epidermis, that of the "Vepreculae" being 

 more compact and parenchymatous and often more smooth and 

 shiny. Of the occurrence of these two forms together, three cases 

 may be cited: In one collection (no. 6515) of 40 plants, all believed 

 referable to Galaxaura maroiuata, found growing together just below 

 low-water mark near Guantanamo Bay, Cuba, 26 have been examined 

 microscopically and of these 26, 13 were of the "Brachycladia" struc- 



