292 NEW FORM OF NETTED CONFERVACEEX. 
he received from M. Decaisne in 1841. It is very like the other 
species in outward appearance. It is pale brownish-white when dry. | 
The specimen does not show any indication of the imbricate base as 
described by Decaisne, but it is not in a very good state, not being 
well dried. It is inscribed “ Microdictyon Ayardhianum, Dec.," and 
the second label adds Kz. Sp. p. 512. n. 1. 
MACRODICTYON. 
Frond expanded, netted, uniform, without any main filament, entirely 
formed of uniform small elongated joints united so as to form a net- 
work, the sides of the mesh being each formed of a single joint ; 
chlorophyll glandular. It differs from Microdictyon in having no 
main filament from which the other arises. This marine Conferva 
is like a large-jointed Hydrodictyon, but the frond is expanded, and 
not forming a tube. e frond is extended by the new joint spring- 
ing out at the junction of two cells, which is elongated into a branch 
of oblong joints giving out two large oblong cells, one on each side 
of each articulation ; these no doubt at length united to other cells, 
and forming a network. 
Macrodictyon clathratum.—Microdictyon clathratum, Martens. Mi- 
erodictyon Velleyanum, Turner in Herb. Lenormand. Has. Sumatra, 
Pulo Tikus, Martens; Sandwich Islands, M. Edu. Jardine, 1855. 
The development of the cells is like that of Struvea plumosa, as 
figured by Harvey, Phyc. Austral. t. 32. It differs from Struvea in 
not having any central continued midrib or stem, and therefore ap- 
pears more allied to Confervacee than Valoniacee. The genus wants 
further examination, but I do not feel myself at liberty to wet M. 
Lenormand’s single specimens mounted on tale. 
ere is a second specimen forming a large mass roughly dried, 
which appears to be the same plant. It is inscribed Microdictyon 
Velleyanum, Decaisne, forma juven.? Sandwich Islands, M. Edu. 
Jardine, 1855, n. 218. The cells are the same size and form, and the 
whole plant very different from any species of Microdictyon. The mesh 
is much larger, the cells several times thicker and longer, and with the 
green granules well developed and of a larger size. The plant is also 
growing on a Rhodosperm with a stichidia like a Dasya or Polysi- 
phonia, but the fragments on the specimen only show the stichidia. 
I cannot see any appreciable difference between the specimen from 
