CALCAREOUS ALGAE OF THE MIDDLE EAST 



EXPLANATION OF PLATES 



Unless otherwise stated, all material is housed in the British Museum (Natural 

 History). 



calcification shown : this feature is variable between different known genera. 3. 

 Clypeina : separate fossil disc and reconstruction of living plant (Permian to Oligocene). 

 Separate whorls of naked sterile branches and fertile whorls of fused, heavily-calcified 

 branches. Shape and fusion of discs or cups variable between species. 4. Segment of 

 Cymopolia eochoristosporica Elliott (Upper Cretaceous), and separate branch-diagram. 

 This species transitional between cladospore and choristospore, showing as a small 

 cymopoliform branch-system developing on the end of a swollen cladospore branch. 

 5. Segment of Cymopolia sp. (Tertiary) and separate branch-diagram, to show typical 

 choristospore branch with separate sporangial body at junction of primary and secondary 

 branches. Cymopolia is segmented and heavily calcified, but other choristospore genera 

 exist which are single (non-segmented) and more lightly calcified. 6. Sketch of portion 

 of Halicoryne (Recent) to illustrate choristosporic organization with different proportions 

 and arrangement of the component elements. The large elongate gametangium (left) 

 is paired with a much smaller sterile branch-system, the whole whorl grouped in a loose 

 basket-like circular arrangement. Light incomplete calcification only. 7. Acetabularia 

 (Recent). Plant showing typical mature calcified reproductive disc and stem, also 

 diagrammatic cross-section of disc. This may be regarded as a fused calcified structure 

 analogous to that of Halicoryne (note small sterile branches) : the scars of early sterile 

 whorls may be seen on the stem. Acetabularia is thus the choristosporic disc-analogue 

 to the cladosporic Clypeina, as now interpreted. 



