5i6 



INTRODUCTION TO PLANT GEOGRAPHY 



[chap. 



or, in some warm seas and brackish lagoons, Blue-green Algae 

 (Cyanophyceae). Examples of typical Diatoms and Peridinians are 

 shown in Figs. 6 and 7, respectively. Thus the brown colora- 



FiG. 171. — Photomicrographs of marine phytoplanktonic communities. A, Early 

 summer ' maximum ' of Diatoms off the Atlantic coast of North America. Domin- 

 ant are Guinardia sp. (short and square) and Rhizosoleiiia sp. (long and slender), 

 (X about 35). (Phot. H. B. Bigelow.) B, Late summer ' peak ' of Peridinians 

 (anchor-shaped Ceratium sp.) and animalcules (pencil-shaped Tintinnids) off the 

 Atlantic coast of North America. ( ;< about 50.) (Phot. H. B. Bigelow.) 



