Chapter X —115— Duality of the Chondriome 



chloroplast (certain Chrysomonadales). According to Chadefaud, 

 the forms possessing only a single chloroplast represent the most 

 primitive types. 



Among the forms without chlorophyll, VoLKONSKY has reported 

 in Polytoma uvella the existence of a single leucoplast per cell, 

 which appears as a fine network spread throughout the cytoplasm. 

 This leucoplast elaborates starch. More recently Miss Rabinovitch 

 found the same organelle in Polytomella coeca. It has been possible 

 to suppress the chlorophyll by various cultural processes in the 

 Euglenas but it has not been possible previously to understand 

 what became of the chloroplasts in the forms deprived of chloro- 

 phyll. In the phylogenetic series, above the flagellated algae are 

 placed the green algae, such as the Chlorophyceae, w^hich often 

 possess only a single voluminous chloroplast. We then progress 

 through the Rhodophyceae, the Characeae and bryophytes to the 

 pteridophytes and phanerogams, in which the plastids are always 

 fragmented into numerous small elements similar to chondriosomes. 



