Johnson : Morphological Trends among Fossil Algae 431 



fossil algae, bring out 2 basic facts. (1) The beginnings of the algae are to be 

 found in very remote ages of geological time, at or very close to, the origins of 

 life upon Earth. They were among the earliest forms of life to appear and the 

 evidence available suggests that each of the major groups started independently, 



Table 1 

 Structural Types 



Simple types 

 Unicell 



Palmelloid and dendritic 

 Coccoid habit 

 Filamentous habit 



Heterotrichous habit (^ creeping basal portion 



(an upright portion above 

 Siphoneous habit 



Advanced types 



Heterotrichous filaments 



Discoid 



Crusts or cushions 



Elaborately erect type 



Compact (uniaxial) 



Compact (multiaxial) 



Foliose 



Tubular 



Table 2 

 Parallelism in Development of Simpler Types of Growth Forms 



probably at appro.ximately the same time, and have developed along more or 

 less parallel courses since. (2) By the beginning of the Paleozoic Era (earliest 

 Cambrian time) roughly 500 million years ago, the algae had developed to the 

 point where the algal population was probably equal to that found today, with 



