THE BROWN SEAWEEDS. 47 



The simpler brown seaweeds, so far as known, multiply only 

 by means of zoospores, which may grow directly into new 

 plants, or, as has been observed in some species, two zoo'spores 

 will first unite. A few, like Ectocarpus (Fig. 28, A), are 

 simple, branched filaments, but most are large plants with 

 complex tissues. Of the latter, a familiar example is the 



FIG. 28. Forms of brown seaweeds. A, Ectocarpus, x 50. Sporangia (sp.). 

 B, a single sporangium, x 150. C, kelp (Laminaria), x %. D, E, gulf weed 

 (Sargassum). D, one-half natural size. E t natural size, v, air bladders. 

 x, conceptacle bearing branches. 



common kelp, " devil's apron " (Laminaria), often three to 

 four metres in length, with a stout stalk, provided with root- 

 like organs, by which it is firmly fastened. Above, it expands 

 into a broad, leaf-like frond, which in some species is divided 

 into strips. Kelated to the kelps is the giant kelp of the 

 Pacific (Macrocystis), which is said sometimes to reach a length 

 of three hundred metres. 



