267 



a more or less plane upper face, the cavity being entirely or for the most part 

 sunk in the frond. Their outer diameter is therefore often difficult to state, but it 

 reaches at least 350//. The cavity is nearly globular or usually more or less flattened. 

 The ostiole is without or provided with poorly developed papillae in its under part. 

 In some cases the ostiole was found to be excenlric. The sporangia are only placed 

 at the periphery of the conceptacle, the central part being occupied by a conical 



columella. The sporangia are always 



Fig. 188. Fig. 189. 



Z,i7hop/!!/ZZ(i;)i Cora;/i/ia?. "A,' vertical section of sporanginl con- LithophijUmn Coralliiice. A, Vertical sections of 



ceptacle. 20.'>:1. /?, vertical section of upper part of a similar antheridial conceplacles. In A some spermatia 

 one. 350:1. show two nuclei. A 350:1. B 370 : 1 



and age of the frond. In thicker, older fronds the first produced conceptacula after 

 evacuation become overgrown by the continued growth of the surrounding tissue 

 and are later found as empty cavities in the under part of the crust, while new 

 conceptacula are formed at a higher level (fig. 187). 



The antheridial conceptacles are entirely sunk in the frond, not prominent, 

 rather low, with a flat bottom and a shorter or longer orifice. The spermatia are 

 produced at the end of long sterigmata given off from small cells covering the 

 bottom of the conceptacle. The ripe spermatia are globular-ovoid, at one end (the 

 basal one) drawn out in a short point. Two nuclei were distinctly visible in isolated 

 spermatia (tig. 189 A). 



34* 



