— 78 — 



1909. Both in 1907 and 1908 the decrease of the genus in Sep- 

 tember corresponds to a decrease in rainfall. 



Table to show the occurrence of the principal Protococ- 

 cales in Bartons pond, 1906- 1909 (1) . 



(1) Regarding the symtiols, see l'ootnote 1 on p. ">4. 



