Howe: Structural dimorphism in Galaxaura 623 



One of the largest single collections at hand was that made by the 

 writer on Conde Beach, Guantanamo Bay, Cuba, in March, 1909 

 {no. 6460), where nineteen plants or fragments of plants were 

 picked up on the shore (the species is apparently an inhabitant 

 of rather deep water and is found washed ashore or by dredging 

 in 7-18 meters). Of these nineteen, three were antheridial and 

 of the "Spissae" structure, three were cystocarpic and of the 

 "Spissae" structure, tv\'elve were tetrasporic and of the "Cam- 

 eratae" structure, and the remaining one was apparently sterile 

 and of the "Cameratae" structure. Of five plants dredged in 18 

 meters off Ratones Island near Ponce, Porto Rico {no. 7575) y four 

 belonged to the "Cameratae" and were tetrasporic, and one 

 belonged to the "Spissae" and was cystocarpic. Of numerous 

 plants or fragments dredged in 7-10 meters at the mouth of Guanica 

 Harbor, Porto Rico {no. 7005), all of the thirteen examined 

 showed the "Spissae" structure, three or four of them being 

 evidently antheridial, one cystocarpic, and the rest apparently 

 sterile. Of five plants found washed ashore in the harbor of 

 Port Morant, Jamaica {no. 6276), two had the "Spissae" struc- 

 ture and were cystocarpic, while three showed the "Cameratae" 

 structure, though tetraspores could actually be found on only one 

 of the three. In six plants from Barbados, similar to each other 

 in general habit, though not all collected at the same time and 

 place, five were "Cameratae," four of them with obvious tetra- 

 spores, while the sixth showed the structure of the "Spissae" 

 group and was cystocarpic. On the coast of Florida also, in the 

 region of Jupiter Inlet, Indian River, and Lake Worth, in plants 

 that are somewhat larger, coarser, and longer-segmented than the 

 typical Galaxaura ohtusata, the same correlations may be observed. 

 Finally, it is to be noted by consulting Kjellman's monograph, 

 that all of the species that he placed in the group "Cameratae," 

 in so far as their mode of reproduction was known to him, are 

 tetrasporic, while of the "Spissae" the one species of which the 

 reproductive organs are described is cystocarpic. 



For complete proof that the "Cameratae" structure is a con- 

 stant characteristic of the tetrasporic plants of Galaxaura obtiisata 

 and its allies and that the "Spissae" structure is likewise a constant 

 character of the sexual plants, it would of course be desirable that 



