PH ZOPUYCEAL 77 
increasing in length upwards and the blade is growing 
at its base. The Lessonia type, to which the genera 
Dictyonewron, Postelsia, Nereocystis, and Meacrocystis 
conform, is characterised by greater coinplexity of 
fronds, which are branched in all cases except 
Dictyonewron, and this branching originates in a 
splitting at the growing-point; causing unequal 
divisions in Iacrocystis and equal ones in the other 
Ss 
Fic. 13.—Laminaria digitata. Lic. 14.—Agarum Turneri. 
Reduced. Reduced. 
genera. In Lessonia, which has numerous blades 
borne at the ends of the dichotomously branching 
stalk, and as many growing-points as there are 
blades, the branching arises in consequence of a 
longitudinal slit in the middle of the growing-point. 
This slit in the growing-point at the base of the 
blade extends, or appears to extend, both upwards 
and downwards as the blade and the stalk increase 
