Splacknidium rugosiim. 5 



character of its wall this becomes an exact copy of the apical cell. The 

 basal process grows between the cells of the thallus towards the centre of 

 the branch ; at its extremity it is club-shaped, and in some cases is united 

 to one of the cells of the large filaments, which forms a small outgrowth at 

 the point of contact (plate III., fig. i). It appears to us that this junction 

 may form a point of contrast with the vegetative apical cell described above, 

 and we may perhaps note a further although slight distinction in some indi- 

 cation of casting of the external layers of the mucilaginous wall in the latter 

 case fplate II., fig. 4), which we have never certainly observed in the concep- 

 tacles. This peculiarly modified cell of the conceptacle is homologous with 

 the initial cell of Prof. Bower,* but it undergoes no division and no further 

 development. The epidermal cells lying round it undergo division, and 

 the neighbouring cortical cells increase in size. These causes combine to 

 place the initial cell in a depression (plate II., fig. 7). Hairs arise from 

 the youngest epidermal cells, while others, which were formed earlier, 

 surround the mouth. At this stage, therefore, a young conceptacle is a 

 cylindrical depression in the thallus, with older hairs lining the mouth, 

 while young hairs are being produced round its sides, and the upper part of 

 the initial cell has come to stand out prominently from its base. There 

 is thus a marked contrast with the sexual conceptacle of Fucus serratus. 

 In Splachnidium rugosuni the hairs arise while the formation of the con- 

 ceptacle is in progress, and older hairs line the ostiole, which is never 

 closed, while in Fucus serratus a young conceptacle with a very small 

 ostiole is formed before the appearance of any hairs. In this plant also 

 the initial cell shrivels and finally almost disappears before the production 

 of any hairs ; in Splachnidium rugosuni the initial cell remains a most 

 prominent object in the conceptacle till it has reached maturity. 



By repeated radial division of the lining cells the conceptacle gradually 

 enlarges, and the base comes to be of greater circumference than the 

 mouth ; the form of the conceptacle is, however, never flask-shaped, with 

 a small ostiole, as in many Fucacece. The hairs which are developed from 

 the lining cells are long, septate, and unbranched, and they increase in 

 length by successive divisions at the base. At this stage the conceptacles 

 present the appearance of the Fasergriibchen of many Fncacecz, the tufts of 

 hair extending a long distance beyond the ostioles (plate III., fig. 3). Later 

 reproductive organs are produced among the hairs in the form of long club- 

 shaped sacs filled with numerous spores (plate III., figs. 4 and 5). We shall 

 speak of these organs as sporangia. The number of sporangia in a single 

 conceptacle increases with its age, and in a mature conceptacle the hairs 



* Formation of the Conceptacles in the Fucacccc. Q.J.M.S. iSSi. 



