203 
Erythroclathrus pellitus Liebman in Flora Danica, tab. 2317, fig. 2, 1840 (sterile). 
Hildenbrandtia rosea Kützing, Phycol. generalis, 1843, p. 384; J. Agardh, Spec., II, pars 2, 1852, p. 495. 
Hildenbrandtia sanguinea Kützing, Phycol. generalis, 1843, p. 384, tab. 78, V. 3 
Hildenbrandia Nardi Zanardini, Synops. Alg. in mar. Adriat., p. 238; J. Agardh, Spec. II, p. 494. 
When young, the crusts are nearly orbicular, or with a more or less lobed 
margin. Å number of such young crusts frequently fuse together into a large crust, 
leaving no traces of the limits between the particular crusts. On the other hand, 
older crusts may, when meeting, be separated by a very distinct limiting line. 
The margin is composed of radiating filaments, the ultimate cells of which 
are long and almost colourless, frequently swollen at the end. Not only the outer- 
most cell, but also the second cell from the 
border may be several times as long as broad, 
longer than the next inward following cells 
of the basal layer, from which it must be 
concluded that intercalary divisions may occur. 
Now and then the number of the cell-rows 
RR SE DOG) 
is increased by ramification. The fig. 121 A û 8 N 
suggests that the cell-rows may branch by Song 
dichotomy; but a closer examination showed B 
that their ramification is really lateral (fig. Fig. 121. 
Len ee g . o y Hildenbrandia prototypus, borders af young fronds, 
121 B. The crust represented in this figure seen from the under face. A 350:1. B, showing 
showed numerous lateral branches, some of  thelateralramification and some branches growing 
which penetrated between and under the pri- RE NTI EN LORD: 
mary filaments, in the latter case causing irregularities in the structure of the basal 
layer. In other cases this layer showed a very regular structure; it is densely 
appressed to the substratum, without rhizoids. 
Horizontal divisions occur at a small distance from the margin. The adult 
frond is composed of regular vertical rows of nearly cubical cells, which are 4 to 
6,5 broad. The cell-walls are firm, not swelling at the death of the cells. There 
is a single calotte-shaped chromatophore situated in the upper part of the cell 
(fig. 123 C). 
The tetrasporangia occur in immersed conceptacles, which often occupy the 
whole crust except the marginal part and are uniformly spread over it, but may 
also be arranged in groups. In a fully developed state, the nemathecia are nearly 
globular or a little depressed, about 100 in diameter. The sporangia are situated 
on the bottom and the sides, and even on the under side of the peripheral part of 
the roof, the thickness of which diminishes towards the aperture. The conceptacle 
is not prominent; on the contrary, the surface is often a little sunk towards the 
aperture. 
The conceptacles arise from a small group of superficial cells which produce 
tetrasporangia, while the contiguous cells remain vegetative and continue dividing 
by horizontal walls, with the result that the sporangia are placed in a low cavity. 
26* 
