198 
THE SPORANGIA OF HALIMEDA., 
- By Eruent §. Garp. 
(PLate 461.) 
some marine alge sent me by Dr. Herdman in 1903 
Harv. bearing sporangia, and, as these had never been previously 
recorded for this species, I published a note on the subject, together 
with a list of the remaining alge, in Dr. Herdman’s Report on the 
Pearl-Oyster Fisheries (Roy. Soc. 1908, Suppl. Report, 1. pp. 163- 
67). Comparisons were there drawn between the sporangia of 
, H. gracilis and those of H. Tuna, as described and figured by Derbés 
& Solier (Comptes Rendus, Suppl. p. 46, tt. 11, 12 (1856)). Fruiting 
specimens of H. Tuna are very rare in herbaria, and, as I had never 
had an opportunity of examining one, it was impossible to clear up 
several doubtful points, or to make a complete comparison between 
the sporangia of the two species. However, thanks to the kindness 
Mons. Ed. Bornet, who has lately sent me a portion of the 
identical specimen of H. Tuna described by Derbés & Solier (J. ¢.), 
it is possible to add some information regarding some of the obscure 
points 
rruee ee. 
3 
Description of Thallus.—Before proceeding to describe and com- 
pare the fruiting joints of H. Tuna and H. gracilis, it will be as 
well to recapitulate the description of the internal structure of the 
7 thallus of Halimeda. 
___. Itmay be remembered that the thallus of Halimeda is composed 
_ of unicellular branching filaments, which form three distinct layers 
in each joint: 1. A strand of filaments which runs up the axis of 
the plant from the root to the apex. 2. A network of branched fila- 
ments, the subcortical layer, derived from the side branches of the 
quite free from one another. At the apex communication is estab- 
lished between the filaments in one of three ways :— 
. In some species, as was shown by Prof. Askenasy (Forsch- 
ungsreise, 8.M.S. ‘Gazelle,’ Th. iv. Bot. Algen (1888) ), openings 
or pits are formed in the adjacent walls of all the filaments, and 
Journan or Borany.—Vow. 42. [Jury, 1904.] Oo 
