12 BOTANICAL GAZETTE [january 



(8) discovered that Dictyota had definite periods for the development 



of its fruit. This is well explained in his introductory paragraph: 



"While studying the development of the sexual cells in Dictyota, 



the interesting discovery was made that the process was practically 



simultaneous, not only for a given plant but for all the plants of the 

 locality." 



This work by Williams was done at Bangor, Wales, and at Ply- 

 mouth, England. During the summer of 1906, observations were 

 made on the same plant at Beaufort, North Carolina, by W. D. 

 Hoyt (4): "It was found at Beaufort, also, that this alga produced 

 its sexual cells in regular, periodic crops One observation is 



interesting in this connection. A female plant kept in the laboratory 

 for nearly two months and then examined showed sori only slightly 

 less advanced than those on plants growing in the harbor 



1 ms result is similar to the one observed by Williams but goes a 

 step farther in showing that periodicity is transmitted to new struc- 

 tures formed from the original plant, even where these are not sub- 

 jected to alternating conditions It still remains to be seen 



whether the periodic habit can be transmitted through the nroto- 



asm 



Spirogyra under artificial environment 



experiments were conducted 



windows were used which faced toward the northwest, northeast, 

 and southeast. Whenever a new line of investigation was begun, 



aquaria 



One set was 



placed in a northwest, one in a northeast, and one in a southeast 

 window. The conditions made use of in the three sets of experiments 



temperat 



experiments 



and a difference in light intensity. Other „_ WM 



ducted which had nothing to do with conditions of "temperature and 

 light. 



In the first experiments Spirogyra was brought into the laboratory 

 and small amounts placed in aquaria filled with water from the 

 pond from which the plant was taken. In some cases the plant was 

 washed before being transferred to the aquaria, in others it was not. 



A second group of experiments contain^ th* M m — ^™* 



















I 













