19 



of the substratum. This specimen, however, is on the whole somewhat differing, and only bears 

 a solitary conceptacle of sporangia which is but slightly developed. 



On a radial section of the crust the hypothallium appears vigorously developed, but the 

 cells are smaller, than usual vvith species whose crusts develop themselves 

 partially freely. The central cells are mostly but slightly elongated, 8 — 15 

 or up to iSu.. long and 6 — 1 2 ;;.. broad and sends forth upwards rather 

 long bent dichotomous rows of cells, but downwards short ones. It is, 

 however, to be noticed that for the time I only possess somewhat oblique 

 sections which are not properly representative of the structure of the 

 hypothallium. The perithallium is also vigorously developed and either 

 not stratified or indistinctly so to judge from the material examined. The Lithothamnion proiif er YoA. 



,. r , . . i-i 11 i-ii Vcrtical section of the 



cells of this layer are square, mostly with rounded corners, slightly pe rithaiiic layer- x 72. 

 elongated horizontally or vertically, 4 — 7 u.. in diameter, or more definitely 



vertically elongated, 7 — 10 or sometimes up to 12 u.. long. The walls of the cells are generally 

 fairly thick (Fig. 8). 



The reproductive organs known are sporangia. The conceptacles are subprominent or 

 in part but very slightly raised above the surface of the plant, finally rather flattened, 800 — 1 100 u. 

 in diameter, when seen from above. They are partly not sharply defined. The roof is intersected 

 with about 100 muciferous canals. The sporangia are four-parted, 150 — 200 by 80 — 100 p.., 

 with enduring partition walls. The plant is sparingly furnished with these organs in the 

 month of June. 



This species is found associated with Lithothamnion fragilissimum and L. simulans, and 

 partly shares substratum with the former. Young specimens resemble L. fragilissimum a little 

 in habit. As to reproductive organs hitherto known it comes very near to L. Philippi. On 

 the other hand the plant is next akin to L. funafutionse, from which species, however, it is 

 distinguished by mostly larger conceptacles and by detaching itself from the substratum. Besides 

 there is some divergency as to structure. 



Occurrence: The species seems to be of no frequent occurrence at the stations 

 mentioned above. It was found best developed at the station 81. 



c. R a m o sa. 



6. Lithothamnion. fruticulositm (Kütz.) Fosl. Fig. 9, ex parte. 



List of Lith. p. 6 (non Norw. Lith.); Spongites fruticulosa Kütz. Polyp. Calcif. p. 33 et Tab. 

 Phyc. 19, t. 99. Syn. L. fasciculatum /3 fruticulosum Hauck, Meeresalg. p. 274. 



f. pteridoides Fosl. mscr. PI. II, fig. 1 — 4. 



Resembling f. crassiuscula except that the conceptacles of cystocarps are less distinctly 

 defined, lower and with a more distinct acute tip. 

 f. clavulata Fosl. PI. II, fig. 5 — 9. 



Corall. in SCHMIDT, Fl. Koh Chang, p. 17. 



