The Algae 457 



spores, and whose Kfe cycles culminate in the production of 

 oospores and resting spores in March and April. During the 

 summer the vegetative plants disappear and only the spores 

 live over in the mud. 



The spring annuals constitute by far the largest wave of 

 algas. The spores germinate in autumn, winter, and early spring, 

 and reproduction reaches its maximum in May and early June. 

 Most of these plants disappear by July. 



The summer and autumn annuals germinate in spring and have 

 longer vegetative periods before fruiting. 



There are also perennials, like Cladophora, that live over 

 from one year to the next and produce spores at various times 

 of the year. These form the long, green streamers that one sees 

 in swift streams, on dams and waterfalls, and attached to objects 

 in lakes. 



Finally, there are the ephemerals — short-lived unicellular or 

 colonial forms of the plankton and wet soils. Here a new genera- 

 tion may arise every few days. They reach their greatest 

 abundance in late summer. 



Algae are more numerous in seasons when the water levels 

 are high. They also fruit most abundantly under these con- 

 ditions. The periodicity determines what species will be found 

 associated at any time of the year. Ponds that dry up in early 

 spring obviously can have only winter annuals, while ponds 

 that last until June will have both the winter and spring annuals. 



THE BROWN ALG^ OR PH^OPHYCE^ 



The brown algae are with few exceptions marine plants. They 

 possess in addition to chlorophyll a brown pigment which masks 

 the green color. They attain their greatest dimensions along 

 rocky coasts where the temperatures are low. The vegetative 

 body, or thallus, is in many species larger and is far more complex 

 in structure than in the green algae. Some of the plants attain 



