406 PRACTICAL BOTANY 



the formation of this wall is the first obvious change 

 after fertilization. 



2. The elongated club-shape of the older plants. 



3. Their terminal depression, from which numerous 

 hairs protrude. 



4. The mode of attachment by means of hypba- 

 like threads of independent growth, similar to those 

 seen in the older plants : some of these threads 

 may be seen quite young, and not yet attached to the 

 substratum. 



From such plants as a starting-point, intermediate 

 forms will lead on to the mature Fucus plant. 



Laminaria digitata, Lamour. 



The genus Lammaria is so prominent among the Phseophyceae 

 that it calls for a short notice : the various native species of the 

 genus grow near to or below the low-tide mark, and L. digitata 

 is perhaps the commonest of them all. 



Note with the naked eye in fully grown specimens of this 

 plant 



1. The organ of attachment at the base, which produces 

 many branches : these approach the substratum, and attach 

 themselves closely to it. 



2. The elongated stipe, of more or less flattened cylindrical 

 form, with a brown exterior and cartilaginous consistence. 



3. The expanded frond, which is also cartilaginous, and is 

 irregularly cleft into segments. 



4. On some specimens, especially in winter, may be found 

 irregularly thickened, slightly brownish patches, on which the 

 reproductive organs are produced. 



Cut through the stipe transversely, and, smoothing the surface, 

 examine it with the naked eye : if the plant be an old one, there 

 will be seen 



1. A brown peripheral band of outer cortical tissue. 



