F. Borgesen: Rhodophyceæ of the Danish W. Indies. 



125 



As to their outer habit the specimens found show much hke- 

 ness to the figures c and d of Kützing quoted above. 



A transverse section (Fig. 133) of the thalkis reveals the fact 

 that the medullary tissue is very loose and open in the middle 

 more dense outwards. It consists of thin cylindric filaments very 

 irregularly, often stellately, branched and woven together. Their 

 diameter is variable, often 5 — 6 [x thick. Towards the periphery 

 they grow tkicker and mostly run more or less parallel with the 

 surface of the thallus. From these filaments the cortical layer arises. 

 This consists of short dichotomously ramified filaments placed verti- 

 cally upon the surface of the thallus. The innermost cells in this layer 

 are largest, nearly spherical, 

 about 6/i thick; from these 

 is an even transition to the 

 peripheral ones which are 

 subcylindric about 4/z thick 

 and %n long. 



The tetraspores are 

 found in great numbers in 

 the cortical layer over the 

 whole surface of the thal- 

 lus. They are cruciately 

 divided and about 27// long 

 and 14// broad. 



The cystocarps occur 

 scattered, more or less, over 

 the whole surface of the 

 plant. They are nearly sphe- 

 rical about 180/« broad; the 



cells in the wall are of very irregular shape. The carpospores are 

 formed in great quantities and are about 14// broad. 



This species is httoral; it occurs in quite shallow water in 

 rather exposed places where it is dashed by the waves. Like 

 Gr. cuneifolia it is found abundantly in polluted water near the 

 town but it is also found in quite clear water. 



St. Thomas: The Harbour near Charlotte Amalie, the Hurrican Island. 

 Geogr. Distrib. : Mediterranean sea, warmer parts of the Atlantic 

 Ocean. 



3. Grateloupia cuneifolia J. Ag. 



Agardh, J., Algologiska bidrag in Öfversigt k. sv.Vetensk.-Akad. For- 

 handl. 1849, p. 85; Spec. Alg., vol. II, p. 181; Epicrisis, p. 164. Montagne, 

 Sylloge gen. spec. Cryptog., p, 433. Kützing, Tab. PhycoL, vol. 17, tab. 34. 



Fig. 183. Grateloupia dichotoma J. Ag. 



Transverse section of the thallus with 



tetrasporangia. (About 550 : 1). 



