PLATE XIII. 



FI&. PAGE 



1. Desmarestia aculeata 48 



1 a, branchlet of a young frond, magnified. 



2. Cladostephus verticillatus 75 



2 a, whorls of branchlets, magnified. 

 2 b, branchlets, magnified. 



2 c, branclilets with spores, magnified. 



3. Ulva latissirna 257 



3 a, cellules of upper layer of frond, magnified. 



