378 



BOTANY OF THE LIVING PLANT 



marks it lies down flat, and where the growth is dense the plants 

 mutually protect one another from drying. 



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

 an apical cell. In Fucus the growing point lies in a depression at the 

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



FIG. 316. 

 Drawing of an actual plant of Fucus serraius. (J Nat. size.) 



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 Ectocarpeae, and in the more 

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

 Laminaria, where a new frond is formed each season between the 

 old one, which is thrown off, and the persistent stalk (Fig. 317). 



In simple forms the cells are all alike. Soft cell-walls surround a 

 >uni-nucleate protoplast, which includes simple brown chromatophores. 





