— 19 - 



developed ones. They almost coincide in shape with those in L. Plii- 

 Uppii and L. lichenoides , but are smaller , about 500 // in diameter at 

 the base, and apparently as a rule more acute. The central parts of the 

 „ conjugation cell" bear a bundle of somewhat elongated paranemata. 



The present form does not differ much from the Funafuti plant, 

 which I provisionally name f. genuina. The latter has a rosy colour, 

 sometimes with a feeble purplish shade, while f. purpurascens is darker 

 or lighter purplish. The crust is frequently a little thicker and less ir- 

 regular, but on the other hand generally with slightly smaller cells than 

 in f. genuina. So also the conceptacles of sporangia being a little smaller, 

 and in the few ones that I have seen not flattened in the central parts. 



Between Koh Mesan and Gape Liant on a depth of 9 fathoms (not quite 

 certain) ; 15 naut. miles E. of Koh Chuen, 10 fathoms ; the north side of Koh 

 Mesan, 10—15 fathoms; between Koh Mesan and Gape Liant, 5 — 8 fathoms; 

 the north point of Koh Ghang on Coral-reefs; and Koh Kahdat in 2 fathoms 

 water. 



Area: South Pacific Ocean: Funafuti (I genuina). 

 4. L. siamense Fosl. mscr. 



Thallus forming delicate, light rosy, smooth crusts or nearly 

 so on divers hard objects, 80—100^ thick. Conceptacles of spo- 

 rangia convex, rather prominent, 300—500// in diameter. Sporangia 

 four-parted. Conceptacles of cystocarps conical, 350 — 600// in 

 diameter. 



f. minuta Fosl. mscr. 



The crust 30-60 // thick. Conceptacles of sporangia 300— 

 400// in diameter. Sporangia 60 — 70// long, 25 — 30// broad. Con- 

 ceptacles of cystocarps 350— 450/y. in diameter. 



f. si m il la il s Fosl. mscr. 



The crust 50 — 100 a thick. Conceptacles of sporangia 400— 

 500/^ in diameter. Sporangia 140—160// long and 60—80// thick. 

 Conceptacles of cystocarps 500 — 600// in diameter. 



This is one of the most delicate of the species of this genus at- 

 tached to hard objects. It sticks especially to Corals, but is also met 

 with on stones , shells of Mollusks or even attached to other calcareous 

 Algae. The colour is in a dried state a light rosy, sometimes, however, 

 with a greyish-green shade. The crust is at first almost orbicular, here 

 and there with slightly crenulate margin. In an old state it becomes 

 more irregular in outline , and more crusts founded near each other get 

 fully confluent without any visible limit , at length forming an apparently 

 solitary crust up to about 12 mm. in diameter, often, however, much 

 smaller, or but 3 mm. in a fertile stage (f. minuta). But sometimes it 

 almost covers small shells of Mollusks (f. simulans). It is smooth and 

 not or very feebly shining. The smoothness of the crust depends how- 

 ever on that of the substratum, although it appears sometimes to become 

 a little uneven in an old stage even on a plain substratum, partly by 



3* 



