- 18 — 



f. purpurascens Fosl. mscr. 



Thallus forming up to 2 mm. thick crusts on Corals, frequently 

 with wart-like excrescences 2 — 3 mm. in diameter. Conceptacles 

 of sporangia subprominent, 550—700 p. in diameter. Conceptacles 

 of cystocarps subcorneal, about 500^ in diameter. 



In the quoted papers I mentioned a calcareous Alga from Funafuti 

 which I considered a form of L. Philippii. In the collection from Siam 

 are a few mostly fragmentary specimens which certainly differ in habit 

 from the Funafuti plant , but on the whole are closely related to this. 

 On the other hand, also the latter form much approaches L. Philippii. 

 However, as both show almost the same divergences in their relation to 

 L. Philippii, it appears that they must be considered as forms of a 

 separate species. Both cling more firmly to the substratum than L. 

 Philippii, the latter even sometimes almost loosens itself and develops 

 rhizoids in the lower part of the frond which occasionally at length form 

 small fronds as in Lithophyllum expansum. The conceptacles are smaller 

 than in the said species , although in this respect no true limit is to be 

 drawn. Besides, as mentioned in the quoted papers, the hypothallus 

 differs rather much from that in L. Philippii , being more feebly deve- 

 loped with more narrow and thin-walled cells than the generally thick- 

 walled cells in the latter. I have seen but some few specimens of L. 

 Philippii. It seems to be rather varying , and the limits are not yet 

 fully known. Perhaps it even includes more than one species in the 

 sense formerly taken. This cannot be decided till a larger material is 

 procured than that I at present possess. I think however to be entitled 

 to adopt the said forms as specifically distinct. 



The form purpurascens sticks especially to divers Corals. It forms 

 more or less extended crusts up to about 2 mm. thick , frequently how- 

 ever thinner. The crust is more or less uneven and feebly shining, 

 generally with wart-like excrescences 2 — 3 mm. in diameter, or some- 

 times thinner, scattered and branch-like processes appear at least in part 

 by covering up small extraneous objects or penetrating animals. A new 

 crust occasionally is formed upon the primary. 



With reference to structure the cells of the feebly developed hypo- 

 thallic layer are elongated and up to about 20 fi long, with thin walls 

 or rather so. The lower anticlines form a slow T convergence towards 

 matrix. The cells of the perithallic layer are much varying in shape and 

 size, and often without any distinct order, partly but 4 — 5 by 5—6 /j. 

 in diameter , square or rounded , not seldom with the longest diameter 

 in horizontal direction, or especially upwards square or more frequently 

 vertically elongated, 7 — 12 fi long and 5 — 7 fi broad. 



The reproductive organs in the present specimens of this form are 

 very scanty and not well developed. I have seen but a few conceptacles 

 of sporangia and cystocarps. The former are slightly convex but little 

 prominent, 550 — 700 a in diameter and intersected with a number of 

 delicate muciferous canals. The sporangia are four-parted, judging from 

 a solitary conceptacle examined 140 — 170 fi long and 60 — 70 fi broad, 

 with apparently enduring interwalls. The conceptacles of cystocarps seem 

 to be rather varying, although I have seen but a couple of almost fully 



