213 



by RosANOFF (1866 p. 70), but as. shown by Solms (1881, p. 24), they are really 

 hairs or hair-producing cells. They are easily recognizable after the hair has been 

 shed, showing a scar left by the latter; I propose to name them trichocytes or 

 hair-cells. 



The sporangia are always divided by one or three transversal walls, dividing 

 the cells into two or four spore-cells. Vertical divisions I have only found as rare 

 exceptions in Lilhothamnion Sonderi (fig. 137 E, F). The tetrasporic sporangia are 

 first divided by a transversal wall, but the formation of this wall proceeds slowly 

 from the periphery towards the centre, and the formation of the two following 

 walls has frequently begun before that of the first is completed. In Corallina offi- 

 cinalis I found that the primary nucleus of the young sporangia divides into four 

 nuclei which arrange themselves in a longitudinal row in the middle of the spor- 

 angia, and that these rest for a long time in this stage before the divisions, which 

 take place almost simultaneously (fig. 197). Also in Epilithon meinbranaceum the 

 three divisions are almost simultaneous (fig. 152, comp. otherwise fig. 134). The di- 

 viding wall is shown in figs. 131 B and 142. 



The number of spores is constant in most of the species, either 4 or 2; but in 

 some species both disporic and tetrasporic sporangia are met with. One of these 

 species is Lithoihamnion Iceve which, however, in the Danish waters has only been 

 found with disporic sporangia. The above mentioned fact that the divisions of the 

 tetrasporic sporangia are, at least in several cases observed, almost simultaneous, 

 makes it improbable that the disporic sporangia can here be interpreted as unripe, 

 not fully divided. It is an incontestable fact that some species may, according to 

 circumstances, have tetrasporic or disporic sporangia. This I have also found to 

 be the case in L. Lenormandi, in which only tetrasporic sporangia were previously 

 known. In Melobesia Fosliei also, and in M. minutula, both kinds of sporangia would 

 seem to occur. 



In material fixed in Juel's liquid the protoplasm of the tetraspores showed a 

 foamy structure. The central part containing the nucleus was brighter and distinctly 

 marked off from the outer (figs. 132, 142 B and Plate III fig. 1). 



The antheridia present considerable differences as to their position and devel- 

 opment. In Lithoihamnion Lenormandi they have a similar position to that pre- 

 viously described in L. polymorphum, being produced on the surface of great bushes 

 extending from the periphery towards the centre of the conceptacle (Plate III fig. 2). 

 If this structure is to be found in all the species of the genus, we have here an 

 important generic character. In Epilithon membranaceum, referred by some authors 

 to the genus Litliothamnion, the antheridia are, as shown by Guignard (Rev. gen. 

 de Bot. I. 1889, p. 182) seriate in short filaments clothing the bottom of the con- 

 ceptacle, and in the other genera the antheridia (spermatangia) are also placed on 

 the bottom of the conceptacle, being produced as outgrowths from a layer of small 

 cells, but they are not seriate. The antheridia are more or less lengthened, short 

 cylindrical or upwards somewhat thickened and more or less curved. In Melobesia 



