1909] COP ELAND— PERIODICITY IN SPIROGYRA 19 



several feet. Vaucher says that this species conjugates from Febru- 

 ary 20 to April 1 2 ; Petit gives April-May. In the ponds mentioned 

 this species appeared in July and with increasing abundance until 

 early in August. The first fruiting specimens were collected August 

 2, and the last August 21, and neither vegetative nor conjugating 

 filaments as late as September 1. 



Spirogyra Lutetiana (P. Petit).— I was not able to identify this 

 species except in a single locality. Its habitat was a small open ditch 

 in a meadow unprotected from the sun. Petit gives the fruiting sea- 

 son as March-May. The only date at which I found it in a state 

 of conjugation was October 14, and when collected it had all the 



erial which had fruited earlier. This 



ma 



Sp 



month 



writes: "I 



have found this species fruiting abundantly in May. When 



mass 



as follows: " 



May; forming 



Wolle agrees 



green masses." I have found this species in fruit in seven different 

 localities. The first date for each was as follows: May 1, May 2, 



July 3i, July 



Those fruiting 



weeks 



in May were found in rather sluggish streams and in water varying 

 in depth from one to four feet ; those fruiting in July and August were 

 in cattle tracks and in a small ditch. The conjugating period in the 

 spring lasted about four weeks ; in the summer the period was about 



temperature of the water in the former ponds varied 

 from 12 to 18 C; in the latter places from 22 to 28 C. All seven 

 ocahties were situated where the plant was protected from direct 

 sunlight for a part of the day. 



Spirogyra orthospira (Nageli).— I had an excellent opportunity 

 to watch the life-history of this species in a small pond of about 



in area, two to four feet deep, and well shaded with low 

 -I he surface of the pond was entirely covered with Spirogyra 



t° a depth of several inches. 



May 



1 ~~« ^U -LT-i-CXJ <C* XL VVCVO XV/C4X1VJ. LW U\* AAW*xvxi.i & 



undantly both at and beneath the surface. It reached its maximum 



a out the second week of June, and by June 30 either vegetative or 



onju gatlng fi laments could be found examining the debris at 



the bottom of the pond. 



