Metaphyta Fucus. 8 3 



sex, which unite together, the product of union developing 

 into a new thallus. 



Taking a general view of the allies of Spirogyra, we find 

 that they embrace a most varied collection of forms. The 

 modification lies principally in the form of the thallus. For 

 example, some take on the form of a hollow sphere, the 

 component cells being provided with flagella, as in Pan- 

 donna. Others again, such as the Coleochcetece, by succes- 

 sive division, assume the form of rounded or irregular plates 

 built out of branched multicellular threads. 



The familiar though aberrant Chara is more thread-like 

 in form, but the delicate stem and branches into which the 

 thallus is divided are more highly differentiated than those 

 of the filamentous forms of which Spirogyra is the type. 



All the forms mentioned are inhabitants of fresh water, 

 and differ only in the structure of the thallus, as above stated, 

 and in the nature of their reproductive cells and the parts of 

 the thallus which bear them. All shades of differentiation 

 are exemplified, from the simple form we have just ex- 

 amined to the fully developed sexual apparatus we are 

 about to describe in the next vegetal type that falls to be 

 discussed. 



SECTION II. SALT-WATER ALG&FUCC7S. 



In this and succeeding vegetal types where the repro- 

 ductive organs are distinctly differentiated, it will be most 

 convenient to discuss the plant first from a vegetative point 

 of view, and then to treat of its reproductive apparatus. 



Vegetative organs. To illustrate the group of salt- 

 water Algae, or seaweeds, and as giving a good instance of a 

 typical plant of the lower or less advanced type, of structure, 

 no better example could be found than one of the common 

 seaweeds Fucus platy carpus. The plant consists of a much- 

 branched and flattened thallus attached by means of cylin- 

 drical and branched roots to some fixed object. The 



G 2 



