Notes. 
269 
order that the thick end may sink, instead of floating uppermost, as it 
would if the specific gravity were the same throughout. Both kinds 
of embryo, the thick and the slender, float in the same way. 
On reaching shore the embryos are planted by the insinuation of 
the root-tip into any softness or crevice of the bottom by the falling 
tide. The figure represents a section of the rock of the shore across 
a crevice, which is full of mud, as shown by the dark shading. The 
vertical embryo is in the position in which it floats freely. The tide 
has fallen until its root-tip engages a projection on the bottom. The 
ripples will now cause its oscillation about the tip, which will thus be 
kept slowly boring down into any mud or crevice present as the 
