APPENDIX. 



LIST OF SPECIES NOT HITHERTO DETECTED IN BRITAIN. 



HYALOTHECA, Ehr. 



3. H. ? duhia (Kiitz.) ; filament without a mucous tube ; joints rather 

 broader than long, with two puncta near each margin. 



Hyalothecal duhia, Kutzing, Phycologia Germanica, p. 140 (1845) ; in lit. 

 cum icone. 



Nordhausen, Prussia, Kutzing. 



Tab. XXXV. fig. 16. portion of a filament from a drawing by Professor 

 Kutzing. 



DESMIDIUM, Ag. 



3. D. undulatmn (Corda) ; joints with four crenatures at each margin. 



Besmidium undulatum, Corda, Observations Microscopiques sur les Ani- 

 malcules des eaux et des thermes de Carlsbad, p. 19. t. 4. f. 27 (1840). 



Carlsbad ; Prague ; and Reichenberg, Corda. 



The constriction of the joints is marked by slight marginal notches, on each 

 side of which are two broad crenatures. 



Desmidium undulatum appears to be a distinct species, differing from D. 

 Swartzii by having bicrenate segments. 



4. D. didymum (Corda). 



Desmidium didymum, Corda, Aim. de Carlsbad 1835, p. 123. t. 4. f. 43. 

 Kiitzing, Phyc. Germ. p. 141. 



Carlsbad, Corda. 



Ehrenberg and Meueghini unite J)esinidium didymum (Corda) to D. bijidum 

 (Ehr.), which the latter describes as a filamentous plant. Kutzing removes 

 Z>. bijidum to Staurastrum, but retains the present plant in Desmidium, of 



