Postelsia 
iS) 
mn 
On 
large specimens which have not yet begun to 
differentiate the sorus: one of these (Plate XVL., 
Fig. 11) measures 23x6 centimeters with a 
holdfast 13 millimeters. There seems to be 
scarcely any localization of the sorus into a 
definite region of the lamina as in most kelps, 
but almost any portion may develop gonidangia. 
Sometimes the sorus occupies a small oval 
patch with fairly definite margins, near the 
base of the lamina; again it may cover almost 
the whole lamina leaving only a narrow mar- 
gin all around. But more often it is irregular 
in shape especially at the distal end. Very 
often instead of bearing a single fruiting area 
the lamina has a series of parallel stripes of 
fructiferous tissue separated by similar sterile 
stripes; these may number as many as five. 
Bot sides of the lamina are fertile, but there 
is no close correspondence between the sori 
of the two as may beseen from Plate XVI., Figs. 
225.0. l “have, a ‘sinele’specimen (Plate XV EL, 
Fig. 6) in which there are two sori, one distal 
to the other, as in Nereocysiis.. The lower is 
a large oval area, 27x5 centimeters, then comes 
