405 
in the greater thickness of their main branches as also in the fact 
that, on a closer examination of the material, sporangia have oc¬ 
casionally been found which were longer in form. In fig. 67 I have 
Fig. 67. Ectocarpus siliculosus (Dillw.) Lyngb. f . arcta (Kiitz.). Different parts of the plant; compare text. 
a, c, d 100 : 1; b 60 : 1; e, f 160 : 1. 
shown some portions of a plant belonging to this form which was 
found in Vaagfjord growing epiphytic on Zostera marina. As may 
be seen the sporangia are in the main short, nearly ovate or oval 
and most commonly sessile, but stalked examples occur intermingled. 
The stalk is sometimes composed of a single cell, sometimes of 
several. Sporangia more long in form occur here and there (fig. 67, 
26 * 
