GEPP—MARINE ALG@X AND MARINE PHANEROGAMS, 397 
HYDROCHARIDACES. 
Hatopuina, Du Petit Thouars. 
54. Halophila ovalis, Hook. f. Fl. Tasman. ii. (1860) p. 45. 
Amirante, 20-25 fms. Seychelles, below 34 fms. Cargados Carajos, 30 fms. 
Gen. Distr. Red Sea. Indian and Pacifie Oceans. 
55. Hnhalus acoroides, Steud. Nomencl. Bot. ed. ii. (1840) p. 554, 
Seychelles: Praslin. On reefs exposed at dead low tide. 
Gen. Distr. Red Sea. Indian and West Pacific Oceans. Tropical. 
Fig. 5. 
Fig. 7. 
Fig. 8. 
Fig. 9. 
EXPLANATION OF THE PLATES. 
Puatres 47-49, 
Microdictyon pseudohapteron, sp. n. 
. Plant, somewhat torn. (Nat. size.) 
- Portion of thallus, showing (a) the stellate mode of branching of the filaments in one plane, 
and (b) the gradual tendency of the branchlets to fill in the meshes of the reticulum 
(x 8); cand d, enlarged diagrams of a cruciate and of a stellate node (x 20). 
. Tenacula which hold the reticulum together. They are expanded crenellated end-walls of the 
branchlet, and are not special cells cut off by a transverse wall, as in Séruvea. One (a) is 
detached, the other (4) is applied to the side of another cell. (x 75.) 
Rhizoids which attach the thallus to the substratum. They are thin unsegmented tubes arising 
from any point of the thallus cells and terminating in a nodulose expansion. a. A group of 
cells with rhizoids in various stages of development (x 40). 6. Single rhizoid (x 110). 
Struvea Gardineri, sp. n. 
Young plant showing main filament branched above by usually cruciate ramification in one 
plane into a reticulate frond with margin entire. (Nat. size.) 
Struvea orientalis, sp. n. 
. Plants showing habit, size, branching of main filament. @. Dried specimen. 6. Specimen 
preserved in formalin. (Nat. size.) The stipes in figs. 5 and 6 is non-septate. 
Portion of frond showing (a) free edge composed of projecting branchlets, and (4) inner part of 
reticulum in which the primary meshes are much filled in by subsequently formed branchlets, 
(x 8.) 
Cells of frond enlarged. a. A primary mesh of the reticulum completely filled in by a 
subsequent growth of branchlet-cells. 6. A few branching cells with a tenaculum. (x 25.) 
Tenacula or specialised terminal cells which fasten the filaments of the reticulum together, 
(x 110.) 
Bryopsis indica, sp. n. 
Fig. 10. Habit of plant, simple and branched. (Nat. size.) 
Fig. 11. Portion of plume showing arrangement of the ramuli alternately disposed in two double rows 
on opposite sides of the main filament. (x 75.) 
SECOND SERIES.—ZOOLOGY, VOL. XII. [ 187 ] o4 
