84 ZYGOFHYCE.E. 



The following is a tabular arrangement of the British species : 

 Sec. 1. Cells not replicate at the ends. 



A. Chlorophyll bands numerous (rarely two). 



* Spores ovoid or elliptic. 



f Membrane smooth. 



1. crassa, Ktz. 



2. jagalis, Dill. 



3. nitida, Lie. 



ff Membrane punctate. 



None. 

 ** Spores orbicular. 



f Membrane smooth. 



4. orthospira, Nag. 



ff Membrane punctate. 



5. orbicularis, Hass. 



6. bellis, Hass. 



B. Chlorophyll bands single or double (rarely ternate). 



* Spore membrane smooth. 



7. porticalis, Vauch. 



var. a. quinina. 



Chlorophyll bands usually single. 

 var. 0. decimina. 



Chlorophyll bands usually binate, rarely ternate. 

 var. . rivularis, Hass. 



Chlorophyll bands usually three. 

 ** Spore membrane punctate. 



None. 



"N.B. Spirogyra elongata, Berk. Glean., p. 33, tab. 12, f. 3 (Rabh. 

 Alg. iii. 241), would follow here but that the fruit is unknown, and heuce 

 it is uncertain. 



C. Chlorophyll bands single. 



* Spore membrane smooth. 



9. condensata, Vauch. 

 - 9. longata, Vauch. 



10. flavescens, Cleve. 



** Spore membrane punctate. 

 (N.B. No record of Sp. velata or Sp. punctata in Britain.) 



Sec. 2. Cells replicate at the ends. 



A. Chlorophyll bands usually two or more, 



* Spore membrane smooth. 



11. Sp. insignis, Hass. 

 ** Spore membrane punctate. 



12. Sp. calospora, Cleve. 



B. Chlorophyll bands single. 



* Spore membrane smooth. 



13. Sp. quadrata, Petit. 



14. Sp. Weberi, Kutz. 



15. Sp. tenuissima, Hass. 



** Spore membrane punctate. 



None. 



