200 PHYLUM V. PHAEOPHYCEAE 
304. Among the commonest of the smaller Brown Algae 
are the species of Ectocarpus in which the plant body is 
composed of simple or branched filaments which may 
attain a length of many centimeters. They 
are firmly rooted below, and their tufted 
filaments float as dark brown masses in the 
tide currents near the shore. They are 
propagated by zoospores produced in one- 
_ celled sporangia which occur on the sides’ 
© het OS of the filaments. These zoospores are 
oval, pointed anteriorly, and have two 
long cilia which are attached near together at one side. 
Generation takes place by the union of isogametes, re- 
sembling the zoospores, but originating in many-celled 
sporangia (gametangia) also occurring on the sides of the 
filaments. This union takes place in the water after 
both gametes have escaped from the sporangia, and it 
results in the formation of a zygote, which soon germi- 
nates and gives rise to a new plant. 
305. The Kelps (Laminariaceew) while large massive 
plants are still of a low type. In the Flat Kelps, or 
Devil’s Aprons (Laminaria), there is a stout stem a cen- 
timeter or so thick, and a decimeter to nearly a meter 
long, firmly rooted below, and flat- 
tened into a broad “leaf” above. 
The whole plant may be a meter or CGE 
even several meters in length, and 3 
the “‘leaf”’ a few centimeters to half AMA? 
a meter in breadth. On the sur- 
face of the “leaf” there develop 
patches of 1-celled sporangia that produce zoospores 
like those in Ectocarpus. Gametes are not certainly 
known to occur in the Kelps. : 
306. Other kelps that are common on the Atlantic or 
Fie. 86.—Laminaria. 
