EE 
ever, a certain number of joints occur which bear only one pinna. On the other 
hand, joints which bear three pinnæ may also occur, though rarely. The pinnæ 
Fig. 306. 
Antilhamnion boreale. Tetraspore- and antheridia-bearing specimen from the Baltic Sea (UL), May. 70:1. 
bear not only pinnulæ along their upper face but also on the under face or on the 
flanks; in the first case the pinnulæ are very often opposite. The pinnæ are more 
