PHTCOPHTTA. 161 



the contents, enclosed in a thin envelope; by this time the 

 protoplasm has divided into four portions, which take on 

 an oval form and develop a crown of cilia. They soon 

 escape from the investing membrane, and after a brief 

 period of activity grow into an ordinary filament in exactly 

 the same manner as the zoospores. 



Practical Studies. — (a) Collect fresh specimens of Sea-lettuce, put 

 into a jar of water, and watch the production of zoospores. Entero- 

 morpha, which is common in brackish waters in the interior, may be 

 substituted for Ulva. 



(b) Study Conferva in like manner. It may be grown in an aqua- 

 rium very easily, so as to be obtainable at any time, even in the 

 winter. 



(c) Collect a quantity of Water-flannel, and put it in a large dish 

 of water, leaving it overnight. Next morning the side of the dish 

 which is nearest to the light will show a green band at the water's 

 edge, due to the myriads of zoospores which escaped during the night. 

 Mount a drop of water and search for zoospores. Occasionally the 

 escape of zoospores may be seen by mounting a number of filaments 

 and searching carefully. 



(d) Specimens of Oedogonium may be obtained by examining the 

 small sticks and stems of aquatic plants from quiet waters. They 

 may be recognized by the enlarged cells (oOgones). 



Systematic Literature. — Wolle, Freshwater Algae of the United 

 States, 65-146. De Toni, Sylloge Algarum, 1 : 1-390. Flora of Ne- 

 braska, 1 : 60-68, pi. n-22. 



Class 3. PnaioPHYCEiE. The Beown Alg^. 



285. The plants of this class are commonly known as 

 the Brown Algae, and Brown Seaweeds on account of their 

 dark color. While they contain chlorophyll, it is more or 

 less hidden by an additional coloring matter, phycophaein. 

 Some of the simpler plants are minute few-celled filaments 

 or masses, but in the higher families the plant-body is 

 large and massive, and many metres in extent. They are 

 almost entirely confined to the waters of the ocean. No 

 members of this class are hysterophytic. They number 

 all told about 1100 species. 



