was also evident in the larger rectangular areas. The random position- 

 ing of .the quadrants and their smaller size probably accounted for the 

 differences in the two studies. 



Figure 9 summarizes the average thallus length (based on 100 specimens 

 per 15 X 9m2) of Avrainvillea nigricans , Halimeda incrassata and Udotea 

 conglutinata at different locations on transect 2. Halimeda showed a 

 substantial increase in length from 15 - 50m. Thereafter, its length 

 fluctuated somewhat, but there was no noticeable difference. Less than 

 20 specimens of Avrainvillea nigricans were found from - 25m. The 

 plants* mean length fluctuated somewhat throughout the remaining portion 

 of the transect, but it was not significantly different. Udotea 

 conglutinata also exhibited limited variation in length throughout the 

 transect. Figures 10 to 12 illustrate the percent frequency of different 

 size classes of fronds of Halimeda , Avrainvillea and Udotea throughout 

 transect 2. From 18 - 36m Halimeda was primarily represented by 

 populations of small plants. Beyond 36m Halimeda was represented by a 

 broader spectrum of size classes and it was relatively uniform to 180m. 

 A comparison of Figures 9 and 11 suggests that Avrainvillea exhibited a 

 relatively consistent population from 27 to 180m. Similar results were 

 evident for Udotea conglutinata , except that it tended to decrease some- 

 what in size from 162 - 180m. 



CAGE EXPERIMENTS 



Although the cage experiments were not of long duration (about three 

 weeks), some interesting results were obtained. A summary of observa- 

 tions is given after 19 days of "regrowth" on June 17. No change in 

 quantity or type of vegetation was recorded for the 3 and 180m cages. 

 Seventeen new plants of Udotea conglutinata were evident under the 60m 

 cage. The plants had an average length of 37mm; they probably re- 

 generated from residual portions of rhizomes in the quadrant. 

 Acanthophora spicif era , Cottoniella arcuata , Dasya pedicellata and 

 Dictyota bartayresii were found for the first time on June 17. 

 Cottoniella arcuata was a conspicuous epiphyte under the cage. Four new 

 specimens of Udotea conglutinata were visible under the 120m cage on 

 June 17. The plants had an average length of 62.5mm. Again, they had 

 probably regenerated from residual portions of rhizomes. Syringodium 

 f iliforme showed conspicuous regeneration on the denuded areas both inside 

 and outside the cages. Three other algae were found for the first time on 

 June 17 (Dasya pedicellata , Wrightiella tiimanowiczi and Dictyota 

 bartayresii ) . Dasya pedicellata was conspicuously reproductive (cystocarpic ) 

 Cottoniella arcuata completely covered the cages and it was a dominant 

 epiphyte on many of the plants within and without the cages. It is of 

 interest to note that all new species found in the 60 and 120m cages were 

 evident in adjacent areas (compare Table 3). 



VI-122 



