LITHOTHAMNIA. 469 



present collection, but on the other hand rather numerous and well-developed specimens of 

 f. typica. 



This species appears to be widely dispersed in the Indian, as well as a part of the 

 Pacific Ocean. Together with Lithophyllum craspedium and L. oncodes it seems to be the 

 "most abundant calcareous alga of the Maldives, and apparently is also rather common in 

 the Laccadives. The plant probably occurs gi-egariously, especially in the lowest part of 

 the littoral zone and upper part of the sublittoral, and is partly attached to corals or rocks, 

 partly either freely developed at the bottom or imbedded in the sand of the sand-flats. It also 

 seems often to loosen itself from the substratum and to continue its growth in the free state. 

 The specimens are provided with reproductive organs in January, although rather sparingly. 



Locality. The Maldives : Hulule, Male atoll, and Suvadiva atoll ; and the Laccadives : 

 Minikoi atoll. 



8. G. Brassica-florida (Harv.) Fosl. 



List of Lith. p. 9; Melobesia Brassica-florida, Harv. Ner. Amtr., p. 111. 



f. laccadivica Fosl. mscr. (Plate XXV. fig. 7). 



Thallus forming crusts on corals 0"5 — 1"5 mm. thick, with simple or sparingly divided 

 short branches, 2 — 25 mm. thick. Conceptacles of sporangia conical, 800 — 900 fi in diameter 

 when seen from above. 



The present plant surrounds a branch of a coral, the latter towards 1 cm. thick, and 

 forms a crust 0'5 — 1'5 mm. thick. From this crust issue crowded in part somewhat anasto- 

 mosing branches which are simple or sparingly divided, fi-equently 3 — 7 mm. long and 2 — 

 2'5 mm. thick, with rounded ends. The branches are now and then knotty. 



The hypothallic layer is well-developed, coaxillate, and the cells frequently 15 — 25 or 

 up to 30 fi long and 9 — 12 fi broad. The perithallic layer forms more or less distinctly 

 stratified layers of tissue, partly with rounded cells 9 — 12 fi in diameter, partly and most 

 frequently with vertically elongated, 12 — 18 fi long and 9 — 12 fi or occasionally 15 /x broad. 

 Here and there appear rows of larger cells. Heterocysts are not numerous. 



The conceptacles of sporangia are to be found somewhat scattered in the branches. 

 They are conical, a little contracted in the middle part, but their more or less elongated 

 upper pai-t falls away at maturity. They are 800 — 900 /u, in diameter, seen from above, and 

 the sporangia are four-parted, 120 — 160 fi long and 45 — 55 /i, broad. 



I have been uncertain whether this plant ought to be considered a form of the above 

 species, or should be regarded as a separate one. Only two fragmentary pieces are known, and 

 these appear to be rather young. The plant is, however, in several respects closely allied 

 with G. Brassicaflorida, and, therefore, I place it as a form of the latter until older specimens 

 may be known. It somewhat differs fi-om typical specimens of the species both in habit 

 and structure, but on the other hand it must be borne in mind that G. Brassicaflorida is 

 a rather varying plant both in habit and even in structure, in the latter respect owing to 

 the fact that it is frequently attacked by lower animals, especially worms, which nearly always 

 show a disturbing influence on the normal development of the layers of tissue. 



It is unknown under what conditions f. laccadivica appears, probably however in the 

 lower part of the littoral zone, or in shallow water in rather sheltered habitats. It bears 

 ripe sporangia towards the end of July. 



60—2 



