— 44 — 



and Cocconeis are not found in Barton's pond, the important 

 Diatoms being Eunotia Arcus, E. lunaris and species of 

 Synedra ; a last peculiarity of Barton's pond lies in the impor- 

 tant part played by colonial Protococcales, Ophiocytium and 

 Flagellata. In fact the algal flora of Barton's pond is far 

 richerand more varied than that of Abbot's pool. Altbongh the 

 geological formation in which the pièce of water lies lias cer- 

 tainly something to do with this, we think that the much more 

 variable water-level of Barton's pond is largely responsible. 

 This leads in the course of the year to a variety of conditions, 

 which probably affords scope for a much greater number of 

 différent forms than would be the case in Abbot's pool with its 

 relatively constant water-level. 



Perhaps the most prominent point of différence between the 

 two ponds lies in the dominance of Clialojihora in Abbot's 

 pool. Barton's' pond however présents conditions, which are 

 quite unsuitable for the growth of so coarse a form, namely 

 the almost complète stagnation of the water and the liability to 

 complète desiccation in the summer months. (Fritsch, 1906, 

 p. 153). We are not aware of any record of ( ïadophora from 

 a pond showing thèse characteristics (cf. Comère, 1910, p. 560), 

 nor do our own observations afford any évidence of the occur- 

 rence of the genus under such circumstances. With the 

 absence of Cladophora there is lost one of the most suitable 

 substrata for the growth of certain epiphytes, and tins may 

 partly account for the non-occurrence of such forms as Cocco- 

 neis in Barton's pond. A second very striking point of diffé- 

 rence lies in the abundant représentation of Confervales in 

 Barton's pond, whereas they are entirely lacking in Abbot's 

 pool. We are at présent unable to suggest any explanation 

 for tins diversity, which in view of the peculiar pigmentation 

 of the chloroplasts in this group of Algae is of considérable 

 significance. 



Mr. Salisbury lias drawn our attention to the unequal distri- 

 bution of the algal flora in Barton's pond. Most algal growth 

 was found near the N.W. bank towards the S. W. end of the 

 pond. Hère the bulk of the filamentous forms occur on the dead 

 inflorescences of the previous year's rushes, while the.stalks of 

 the rushes are covered with a slimy growth of Chaetophora, 

 Budorina, Sphaerocystis and many other colonial and unicèl- 

 lular forms. The best Desmid-material (especially ClosteriuWt 



