PERIODICITY IN SPIROGYRA 



W. F. COPELAND 



The object in beginning these studies with Spirogyra was to get 

 notes on the rearing of species and to see how far they could be 

 changed by conditions. With this end in view ioo aquaria were 

 started and soon contained puzzling results. To interpret these and 

 to get on with the experiments, it soon seemed desirable, if not neces- 

 sary, to know how Spirogyra lives under natural environment. For 

 this reason the major part of my time was given to a consideration of 

 this plant out of doors. An attempt has been made to repeat all 

 observations and experiments under as great a variety of conditions 

 as possible in an ordinary biological laboratory. When field-work 

 was not practicable or necessary, laboratory work was resumed. In 



this way scores of experiments have been in progress from the begin- 

 ning. 



After this work had continued for some months, considerations 

 were given to conditions appearing with some regularity whether 

 Spirogyra was being studied under natural or under artificial environ- 

 ment. As a possible constant condition, it was finally decided to give 

 special attention to the subject of periodicity. In this paper only 

 those experiments will be mentioned which seem to have some bear- 

 ing on this subject. Although laboratory studies are of minor 

 importance in the subject of periodicity, in the present discussion 

 they will appear first. 



in any way aided me 



my 



y. It is a pleasure to thank 

 Dr - C. F. Hodge, who suggested the problem, for his help and criti- 

 cism; Helen Reinherr Copeland for help in identification of 



micr 



W 



lls, Millbury, Mass., for collecting much valuable material in 



that locality; and Dr. O. P. Dellinger, Worcester, Mass., for help- 



ul suggestions and criticisms. The following persons have sent me 



specimens from more distant localities: W 



9] 



Johns 



r, B. A. Place, Iowa 



[Botanical Gazette, vol. 47 



