228 Brown : Algal periodicity 



abundance during the month of January until toward the last, 

 when it began to become more rare and unhealthy. During Feb- 

 ruary and March, the growth became rather rare and unhealthy 

 but showed no signs of fruiting. During April and May, it be- 

 came very abundant and thrifty in its growth, and continued to be 

 abundant until the first of August, being the dominant alga in the 

 pond. There was no indication of fruiting during the year ; con- 

 ditions did not become hard enough to check the vegetative growth 

 . sufficiently to cause the plant to enter the fruiting stage. The 

 fluctuation in the amount of growth from time to time was doubt- 

 less due mainly to change in water supply and temperature. In- 

 creased growth followed warm rains. 



In pond no. 4 Spirogyra nitida appeared for but a short time in 

 October when the pond was low. When rains came, the region 

 was covered with deep water. The alga then disappeared. In 

 pond no. 2, a pond with similar conditions, the growth was 

 similar. 



i 



None of this species was found in the water-works reservoir. 

 It does not seem to thrive in large bodies of pure water nor in 

 pure flowing water. It was rather rare in stream no. I above the 

 campus during October and November, then disappeared. None 

 at all was found in stream no. 2. It was not observed fruiting at 

 any time during the year. 



Spirog) 



1 1 was 



very abundant during a part of the year in ponds nos. 2and 3 and in 

 similar ponds (figure i — chart, pond no. 3). From September to 

 January, this species was rather rare in all the ponds and streams. 

 On January 23 it was found to be very abundant in pools on the 

 ground in open fields in different places where the water had been 

 standing several days. On February 12 it was very abundant in 

 ponds no. 2 and no. 3. It continued to be abundant, in a healthy 

 vegetative condition until the middle of April, when it began to 

 look unhealthy, diminishing considerably in quantity. During 

 February and March, it was near the bottom of the ponds, but 

 when it became unhealthy-looking in April it was floating. Il 

 has not been observed to fruit in these ponds. That found in wet- 

 weather pools has been observed to begin conjugation every time 

 the pools start to dry up. After each rainy period conjugation 



