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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 » in diameter. CGonceptacles 
of cystocarps subconical, 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 » long, with thin walls 
or rather so. The lower anticlines form a slow 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 yp 
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 w long and 5—7 y 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 yw in diameter and intersected with a number of 
delicate muciferous canals. The sporangia are four-parted, judging from 
a solitary conceptacle examined 140—170 » long and 60—70 p. broad, 
with apparently enduring interwalls. The conceptacles of cystocarps seem 
to be rather varying, although I have seen but a couple of almost fully 
