428 ANNUAL REPORT SMITHSONIAN INSTITUTION, 19 3 5 



CONCLUSION 



Just as the higher plants vary in size from the tiny chickweed to 

 the oak tree, so we have found a variation in algae from the micro- 

 scopic unicellular Cystococcus to the giant kelps of the ocean. The 

 number of species is legion. It would require too much space to 

 explain how the life cycle of the algae shows almost every conceivable 

 variant. Algae exhibit an enormous range in structure, reproduc- 

 tion, and life history. They include the simplest unicellular forms 

 as well as elaborate multicellular organisms displaying a considerable 

 measure of division of labor. Perhaps nature was experimenting 

 with this cosmopolitan group of plants, as she placed them in every 

 type of environment. Possibly she learned from them how best to 

 construct her more uniform and more complex group of higher 

 plants. 



Note. — Owing to its considerable size, it was found necessary to omit the 

 list of literature consulted in writing this article. 



The specimens of algae shown in plate 4, figure 2, and plates 5-8 are in the 

 United States National Herbarium. 



