378 



6. Gracilaria usneoides (Mert.) J. Ag. 



J. AGARDH, Spec. Alg., vol. II, p. 595; Epicrisis, p. 415. 



Fucus usneoides Mert. mscr. 



Sphaerococcus usneoides Ag., Spec. Alg., p. 333. 



This species has, according to J. AGARDH, been found at 

 St. Croix by ORSTED and in the Botanical Museum, Copenhagen, 

 some fragments of 0RSTED's plant are kept. These seem to show 

 some likeness to Gr. Wrightii, but they are more densely ramified 

 and the thallus collapses when it is dry. 



Near Buck Island at St. Croix I have dredged a few spec- 

 imens at a depth of about 5 fathoms which perhaps are referable 

 to this species: they show much likeness to Gracilaria Wrightii, 

 but the thallus is softer, the cells have thinner walls and they 

 collapse therefore when dry. 



Geogr. Distrib.: Brazil, West Indies. 



7. Gracilaria Wrightii (Turn.) J. Ag., emend. Collins et Herv. 



COLLINS and HERVEY, Algee of Bermuda, 1917, p. 109. J. AGARDH, 

 Spec. Alg., vol. II, p. 599 including Gr. Poitei (Lam.) J. AGARDH, ibid, 

 p. 596 and Gr. cornea J. Agardh, ibid., p. 598. 



The specimens referred to this species are all coarse, thick 

 plants of cartilaginous consistence. They are ramified very irre- 

 gularly in every direction. 



A transverse section of the thallus shows that it consists 

 of a parenchymatic tissue of roundish, not very large cells, largest 

 in the middle (about 180 H broad) decreasing evenly towards 

 the periphery. The walls of the cells are rather thick and often 

 undulated, especially in the case of the small cells found between 

 the larger ones. Towards the periphery the cells decrease, being 

 about 20 30 (^ thick. A longitudinal section, on the other hand, 

 shows that the cells are rather long, about 170 M, and have thick 

 and sinuated walls. The cortical layer consists of short dichoto- 

 mously ramified filaments composed of small oval cells; at the 

 periphery a rather thick cuticula is found. 



Specimens with tetrasporangia occurred in January and February. 



The plant was found in shallow water in rather protected places. 



St. Croix: White Bay, Lime Tree Bay. Some old specimens from the 

 island are kept in the Herbarium of the Botanical Museum, Copenhagen. 

 Geogr. Distrib.: West Indies, Red Sea. 



