351 



found them a few times in the coherent tissue. They occur in small 

 sori ; later on these sori often merge into smaller groups. When they are 

 found in the coherent tissue the sori, too, merge into rather large 

 groups. When the tetrasporangia are ripe they become free through 

 holes formed by the bursting of the covering cells ; the net gradually 

 dies away and is dissolved. In this way the coherent part of thallus 

 becomes free and is able to give rise to new plants as mentioned above. 



SVEDELIUS has found male plants in the material examined 

 by him. The antheridial stands occur 

 upon the sides of the lamella in the net 

 as roundish, mostly definite sori (com- 

 pare SVEDELIUS, I.e., p. 66, fig. 49); some- 

 times it happens that some of the 

 antheridial groups become connected 

 through the fertilization of the tissue 

 between them. 



I have not found cystocarpic plants. 

 When the plant grows in shallow water 

 it is rather robust, the thallus is broad \2f 



and proportionally short. Sometimes it 

 covers smaller algae e. g. Hypnea, quite 

 densely, forming together with these, 

 roundish tufts. 



In specimens from deep water on 

 the other hand the thallus is thin, Y\%. 346. 

 elongated and narrow. The meshes in 

 the net are large. The lamellae are thin, 

 and proportionally few cross-beams 



are found. Secondary longitudinal lamellae were also found in some 

 of the deep water specimens. 



This species was found in shallow water in somewhat sheltered 

 localities and in deep water in the more open sea down to a 

 depth of about 30 meters. It had tetrasporangia and antheri- 

 dial stands in the months January March. 



St. Croix: Lt. Princess, here often washed ashore; near Buck Island 

 (about 10 meters). St. Jan: In the sound between this island and St. 

 Thomas in several places. 



Geogr. Distrib.: West Indies. 



Martensia Pavonia 

 J. As. Part of the net with 

 tetrasporangia. 

 i M.out 70:1). 



