230 Brown : Algal periodicity 



any evidence of conjugation either between cells in the same filament 

 or with cells in another filament. The spores produced resembled 

 zygospores closely. These were likely aplanospores, such as de- 

 scribed by West * ('04). None of this species was found after No- 

 vember until about the middle of April, when it became abundant 

 in the upper part of the stream. This was not in a healthy vege- 

 tative state. It remained in about the same condition throughout 

 April and early May, not healthy, fruiting to some extent. (Doubt- 

 less this that appeared in the stream in April was washed out of a 

 pond farther up the valley.) wS. varians seems to attain its maxi- 

 mum growth at a temperature considerably lower than that at 

 which £. nitida attains its maximum. 



Spirogyra crassa was found to be rather abundant in a bayou 

 along the edge of the larger of the water-works ponds during 

 August, 1906. This disappeared with the drying up of the bayou 

 in September, and it has not since appeared. On October 12 the 

 same species was found to be rather abundant in an old bayou along 

 stream no. 1. This bayou is about 10 feet wide, 2 feet deep, and 40 

 feet long. It has been formed by the " branch " during high water 

 but is not connected with it directly at present. The alga continued 

 to be rather abundant during October and November and in a 

 healthy growing state. In December it became very abundant, 

 spread out over the pond, sank to the bottom, took on a dark- 

 green color and remained very abundant until the first of May. 

 During the winter it did not grow much, although it seemed to be 

 green and healthy. About the first of May, it was not quite so 

 plentiful, nor so healthy as formerly. Later in May, it disappeared 



altogether. 

 in g- J 



very 



look- 

 Possi- 



bly a certain amount of sewage or chemicals from the chemical 

 laboratory was washed into the bayou during high water a few 

 days before the disappearance of the alga. The alga was not 

 carried away by the water. It did not conjugate. 



but in no great quantities. 



Spirogy 



iflata 



in limited quantity in one corner of the smaller of the water-works 

 ponds where the water was not very pure. Some decaying vege- 



■*^^*^ 1 iii.it . +— *_„ -~^ 



*West, G. S. British Freshwater Algae, 123. 1904. 



