THE ALGE 229 
Specialization of the apparatus for reproduction and differ- 
entiation of gametes are always fownd to accompany progress 
from the lower to the higher stages of plant development. 
294. Summary of the Green 
Alge.—Green alge occur 
almost all over the earth’s sur- 
face. They reach their highest 
development in fresh water, but 
there are many marine genera 
and species, and one of the most 
conspicuous of all the groups 
is that which embraces the sea- 
lettuce (Ulva) and its allies. 
Fie. 159. Part of a ‘‘ Leaf’? of Fig. 158. 
(Considerably magnified.) 
Fie. 158. End ofa Main Shoot 4, antheridium; v, odgonium. At the 
of a Stonewort, Chara. right are a young antheridium and 
(About natural size.) archegonium. 
This plant is a familiar object, waving as it does from 
rocks, piles, and wharves alongshore. Terrestrial genera 
and species of green alge are not uncommon. 
