116 A TEXT-BOOK OF BOTANY 



by other colors, and tne plants have a characteristic grass- 

 green color. As indicated by the illustrations given above, 

 they include simple one-celled forms which reproduce only 

 by cell-division (vegetative multiplication), .and simple 

 or branching filamentous forms which also reproduce by 

 swimming spores and cospores. Such filamentous forms 

 as Ulothrix, Cladophora, and (Edogonium are representa- 

 tives of a group known as the Conferva forms, having 

 bodies of many cells and swimming spores. Vaucheria 

 represents the large group of Siphon forms, characterized 

 by their crenocytic bodies. Spirogyra represents the Con- 

 jugate forms, the name meaning "yoked together," and 

 referring to the connecting of the filaments for fertilization; 

 the group is characterized also by the absence of swimming 

 spores and the peculiar chloroplasts, not all of which are 

 spiral bands. 



The bodies of green Algae are not all single cells or 

 filaments, the marine sea-lettuces, belonging with the 

 Conferva forms, having broad, flat, leaf-like bodies that 

 have suggested the common name. Some of the green 

 Algae are associated with the blue-green Algae in the pol- 

 lution of water reservoirs referred to in 62. 



3. BROWN ALG.E (Phceophycece). 



71. General characters. The two preceding groups are 

 the most common Algae of the fresh waters, but the brown 

 Algae are almost all of them marine. The association of a 

 brown coloring matter with the chlorophyll has given name 

 to the group, and the plant bodies display various shades of 

 yellow, brown, or olive. In size the brown Algae range 

 from forms that are microscopic to those that are hundreds 

 of feet long. They belong chiefly to the colder waters of 

 the globe, reaching their greatest development in the arctic 

 and antarctic regions. The greatest displays of huge bodies 



