Observations on the Cytology of the Chroococcaceae, 
BY 
ELIZABETH ACTON, M.Sc. 
With Plates XXXIII and XXXIV. 
I. Introduction. 
HE controversial question of the structure of the cell in the Myxo- 
X phyceae (or Cyanophyceae) has formed the subject of many papers. 
None of these, excepting Chodat’s (’96) on Chroococcus turgidus , has been 
restricted to unicellular forms, a few have mentioned them incidentally 
along with filamentous forms, while the remainder neglect them entirely. 
Yet it is in the study of the unicellular species, as being the most primitive, 
that one might hope to find the key to the confusion which prevails at the 
present time on this question. 
A detailed investigation of Chroococcus macrococcus , taken up partly in 
order to determine the systematic position of this Alga by finding out 
whether it possessed a fully organized nucleus or not, yielded such un- 
expected results with regard to the structure of the cell that it was thought 
advisable to examine other species of Chroococcus . Later, the investigation 
was extended to other members of the Chroococcaceae. Other species 
examined in addition to Chroococcus macrococcus were — 
Chroococcus turgidus 
limneticus 
minor 
schizodermaticus 
Gloeocapsa sp. 
Aphanothece prasina 
Merismopedia elegans 
„ glauca 
Gomphosphaeria lacustris 
Coelosphaeriu m K u tzingian u m 
Dactylococcopsis sp. 
L Annals of Botany, Vol. XXVIII. No. CXI. July, 1914.] 
