203 



Erythroclathriis pelUtiis Licbmaii in Flora Daiiica, tab. 2317, fig. 2, 1840 (sterile). 



Hildenbraiidtia rosea Kiitzing, Phycol. geiieralis, 1843, p. 384; J. Agardli, Spec, II, pars 2, 1852, p. 495. 



Hildenbrandtia sanguinea Kiitzing, Phycol. generalis, 1843, p. 384, tab. 78, V. 



Hildenbrandia Nardi Zanardini, Synops. Alg. in mar. Adriat., p. 238; J. Agardii, Spec. II, p. 494. 



Fig. 121. 



Hildenbrandia protolijpns. borders af young IVoiuls, 

 .seen from the under face. A 350:1. B, showing 

 Ihe lateral ramification and some branches growing 

 under the primary filaments. 5lj0:l. 



When young, the crusts are nearly orbicular, or with a more or less lobed 

 margin. A number of such young crusis 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 Ihe 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 ibllowing 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 

 is increased by ramification. The fig. 121 A 

 suggests that the cell-rows may branch by 

 dichotomy; but a closer examination showed 

 that their ramification is really lateral (fig. 

 121 B. The crust represented in this figure 

 showed numerous lateral branches, some of 

 which penetrated between and under the pri- 

 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 mai-gin. The adult 

 frond is composed of regular vertical rows of nearly cubical cells, which are 4 to 

 6,5 jj. 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 nemalhecia 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. 



20* 



