255 
The outer part of the sporangial conceptacles (fig. 174 E) is low, wart-like, with 
plane upper face. The outer diameter of the conceptacle is often difficult to state, 
as it is usually for a great part sunk in the frond, and the outer delimitation often 
indefinite. One to three layers of cells are present under the conceptacle. The 
roof is flat, thick, about 5 cells thick. The ostiole is clothed with numerous well- 
developed unicellular hairs, the uppermost of which are long, and protruding out- 
side the ostiole; the undermost ones are shorter and more oblique or horizontal. 
They are all intensely stained by hæmatoxyline. The sporangia do not occupy the 
central portion of the 
conceptacle, where a 
small columella of 
sterile cells is some- 
times to be found. 
The ripe sporangia 
are always tetraspo- 
ric. A small stalk- 
cell is present under 
the sporangia (not 
shown in the figure). 
The antheridial 
conceptacles (fig. 175 
A) much resemble 
those of M. subplana 
(comp. fig. 161), being 
provided with a simi- 
lar tube, and the an- 
theridia having the Fig. 175. 
same shape and posi- Melobesia trichostoma. A, vertical section of antheridial conceptacle. Band C, vertical 
sections of cystocarpic conceptacles. A and C 350:1. B 65:1. 
tion as in that species. 
The cystocarpic conceptacles (fig. 175 B, C) have the same shape and size as 
the sporangial ones, and the ostiole is endowed with a similar peristome. The thick 
roof is plane, or a little depressed near the ostiole. The carpospores are, as usually, 
produced seriately at the periphery of the conceptacle. 
The species appears fairly distinct from all hitherto described species of the 
genus Melobesia. The low conceptacles with the thick, flat or a little deepened roof 
distinguish it from other species of the genus having a well developed peristome 
(e. gr. M. Lejolisii, coronata). Its occurrence on mollusc shells, unusual for the 
genus Melobesia, might seem grounds for placing it in the genus Lithophyllum; 
the want of transversal pores between the frond cells and the fact that these 
cells are not arranged in transversal rows, however, preclude its adoption in that 
genus. 
Locality. Lf: Søndre Ron by Lemvig, near the surface of the water, September. 
