Fertilization in Laminaria and Chorda. 
607 
reason the membrane presents no obstacle to the entry of an antherozoid. 
(A somewhat parallel instance is observable in Pelvetia.) The mouth of 
the oogonium in Chorda remains permanently open. The elongation of the 
young sporophyte is more rapid than in Laminaria , and, in consequence of 
the multiplication of chloroplasts and the development of their pigments 
not keeping pace with growth, the whole plantlet looks much paler than 
the gametophyte from which it has arisen. 
A study of the cytology of the different phases confirms the con- 
clusions arrived at on morphological grounds, that in the Laminariaceae 
we have a case of pronounced alternation of generations, with a great 
reduction in the gametophytes. The cases in Laminaria where the 
gametophyte consists of a single cell separated from the zoospore by 
a single nuclear division make it easy to adopt the suggestion that the 
so-called oogonia and antheridia in the Fucaceae are sporangia. The 
systematic position of the group has to be changed; and we now get rid 
of the anomaly of regarding the alga which shows the highest advance 
in histological differentiation as a member of the Phaeozoosporeae having 
only asexual reproduction. The investigation also furnishes material for 
further consideration of the much-debated question of the relations of 
Chorda to the other Laminariaceae. 
R r 2 
