Brown : Algal periodicity 241 



Vaitcheria geminata var. racemosa was found in pond no. I, 

 October 6 (see chart). It was rather rare, growing in shallow 

 water and fruiting somewhat. During the first of November the 

 pond dried up in parts, but the Vaiiclieria continued to grow 

 freely, forming a dense felt over the rich damp earth on the bottom 

 of the pond. On November 23 this was covered with about a 

 foot of water. The submerged Vaitcheria showed some signs of 

 decay. It remained in about the same condition, unhealthy 

 looking until the twelfth of February, when it was found that the 

 old filaments were covered with fruiting organs. Some of the 

 felts remained attached to the bottom, while others loosened and 

 floated around. They persisted until the last of March, when the 

 filaments turned black and decayed. The pond is surely well 

 sown with spores. The change in conditions due to the flooding 

 with water more than likely caused the formation of the repro- 

 ductive organs. An aquatic form grew throughout the year in 

 stream no. 2 near the spring. Here there was but little variation 

 in the condition, quantity, or temperature of the water. There 

 was no change in the alga. No sexual organs were produced. 



This seems to show that under steady favorable conditions an 

 alga continues in a healthy, growing, vegetative state continually. 

 It was not possible to determine the species of this alga. 



Numerous representatives of the order Protococcales were 

 found but they were nearly all found only occasionally and in very 

 small quantities. On account of this we will pass by all of them 

 except Tetraspora with a mere mention at the end of this sketch. 

 Tetraspora lubrica began to appear in the upper part of stream 

 no. 1 the first of March (see chart). It increased in abundance 

 until the first of May, when it reached its maximum. By the end 

 of May, it had disappeared. This alga seems to thrive in " branch "- 

 or surface-water when flowing freely and at a temperature from 

 5° to 20 C. Certain other colonial forms belonging to the same 

 order, Gonium, Pandorina, Pediastrum, Coelastrum, and Scencdemus, 

 appeared in the more stagnant pools of the upper part of stream 

 n o. 1 during June and July, 1907. 



A number of species of Bacillariales were observed but no 

 effort was made to classify them or trace their periodicity. 



The Cyanophyceae were not very plentiful in the regions 



