BROWN ALGAE 



379 



constructed is well fitted to resist the swirl of the waves, keeping its 

 hold, and though pliant, retaining the form of its leathery frond. 

 Its form gives a large proportion of surface to bulk for exposure to its 

 liquid environment. Plants are normally buoyed up by the water, 



Fig. 280. 



Drawing of a plant of Fucus serratus, showing the fertile 

 distal ends of the longer branches, (i Nat. size.) 



but when exposed between tide-marks they subside to form a dense 

 stratum whereby the plants mutually protect one another from drying. 

 There is in many of these seaweeds a localised apical growth with 

 distal branching. In Fucus the growing point lies in a depression at 

 the extreme tip. In others (Dictyota, Sphacelaria) the apex projects. 

 The segmentation of the apical cell is often very regular, the form and 

 succession of the segments varying in accordance with the form of 

 the tip itself. In other cases intercalary growth is dominant. This 

 is seen in the simple filaments of the Ectocarpales, and in the more 

 complex thallus of Cutleria. But it Is shown on the large scale in 



