Postelsia 
to 
wal 
ioe) 
whether. the two can be separated for there is 
no anatomical character and the texture which 
usually comes to one’s assistance in such cases, 
is not sufficiently different to form a basis of 
separation. The only other kelp whose juve- 
nile forms are likely to be confused with those 
of the present species is Cymathere triplicata 
which is similar to this in structure of the hold- 
fast, a character which separates them from 
most other kelps when still very young. But 
in Cymathere the lamina is much narrower 
and thinner and the folds begin to appear 
when they are 2-3 centimeters in length. 
Histotocy. The thallus of Rewjrewzamis 
composed in general of the same tissues as 
the other kelps. ‘The central- portion onsene 
body is composed of pith-web sharply delimi- 
ted from the surrounding cortex which exter- 
iorly shades into the smaller, more active cells 
of the hypodermis and epidermis. Since the 
histology of several of the kelps has been so 
thoroughly worked out by recent investigators, 
mostly at the Minnesota Seaside Station, it 
will be unnecessary to give a detailed account 
