— 46 — 



Subsidiary végétation of Radiofilum flavescens, Trochiscia 

 reticularis, Ankistrodesmus falcatus, Chaetophora pisi- 

 formis, Gongrosira viridis, Sphaerocystis Schrœteri, 

 Eudorina elegans, Pandorina morum, species of Gloeo- 

 cystis and Ophiocythim cochleare. 



il) Early summer-phase (late .Tune and early July) : Euglena, 

 Desmids, filamentous Conjugatae, Oedogonium, Coleochaete. 

 Subsidiary végétation of Ineffigiala neglecta, Peridinium 

 tabulatum, Bulbochaete ruina and Chaetosphaeridium 

 globosum. 



e) Summer-phase (July, August) : Euglena, Anabaena 

 catenula, Desmids. Subsidiary végétation of Ineffigiata, 

 Sphaerocystis, etc. 



f) Autunm-phase (September, October) : Mixed filamentous 

 flora {Microspora, C,onferva,Zygnema, Mougeotia, Oedo- 

 gonium), species of Oscillaloria and Lyngbya, Trachelo- 

 monas, Sphaerocystis, Ineffigiata, etc. 



g) Early win ter-phase (November): Microspora, Conferva, 

 Diatoms, Trachclomonas. 



Broadly speaking there are four phases, that correspond to a 

 great extent to the four seasons, the other three phases distin- 

 guished above being more of the nature of transitions between 

 the main phases. It is wortli drawing attention to tlie fact that 

 there is some correspondence between thèse algal phases and 

 the phases shown by the Plianerogamic végétation of the 

 pond (1) (p. 40). Thus, the winter-phase with its Microspora 

 and Diatoms corresponds to tlie period in which Eanuncidus 

 aquatilis and Callitriche are the chief représentatives of Plia- 

 nerogamic végétation in the pond; the spring-phase with its 

 Conjugatae, Oedogonium and Conferva is the period of domi- 

 nance of Ranunculus aquatilis; the summer-phase, in which 

 Euglena, Desmids and Anabaena are the dominant algal 

 forms, is characterised by a Plianerogamic végétation in which 

 Lemna, Glyceria and Bidens are successively dominant; 

 while the autunm-phase, which is onlv distinguished in its algal 

 flora by the présence of such forms as Lyngbya and Trache- 

 lomonas, is equally little characterised by its Plianerogamic 

 flora. 



(1) It will be noticed however that, whereas the niost vigorous period l'or 

 tlie algal flora is the spring, it is the summer iu tlie case of the llowering 

 plants. 



