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 papillæ in its under part. 
In some cases the ostiole was found to be excentric. The sporangia are only placed 
at the periphery of the conceptacle, the central part being occupied by a conical 
columella. The sporangia are always 
disporic, 50—88 » long, 18—32 y 
broad. The number of sterile cell- 
layers under the conceptacle varies 
greatly according to the thickness 
Fig. 188. Fig. 189. 
Lithophyllum Coralline. °A; vertical section of sporangial con- Lithophyllum Corallinæ. A, Vertical sections of 
ceptacle. 205:1. B, vertical section of upper part of a similar antheridial conceptacles. 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 ina short point. Two nuclei were distinctly visible in isolated 
Spermatia (fig. 189 A). 
34* 
