114 ELECTRON-MICROSCOPIC STRUCTURE OF PROTOZOA 



Stigmas are lacking. In C. strobilus and C. ericina, an elongate, 

 spindle-shaped pyrenoid occurs centrally in each chloroplast. A 

 very few lamellae or slender paired tubes, apparently continuous 

 with the lamellae, traverse the pyrenoid. In C. chiton, C. minor, 

 and C. kappa the pyrenoid occupies a diverticulum projecting 

 from the chloroplast into the cytoplasm or, in C. kappa, into an 

 invagination of the nucleus. In all species the pyrenoid contains 

 moderately dense, granular or filamentous matrix material and 

 adjacent regions of the chloroplast are of very low density, with 

 few lamellae. The nature of the substance, if any, stored here is 

 unknown; chrysomonads do not store starch. The characteristic 

 photosynthetic product, leucosin, is identifiable by light micro- 

 scopy in large vacuoles in the cytoplasm; these appear empty in 

 electron micrographs since leucosin is extracted by dehydrating 

 alcohols. 



Membrane-bounded lipid droplets, food vacuoles, and 

 microtubular mitochondria are scattered in the cytoplasm of 

 Chrysochromulina. A surprisingly large and elaborate Golgi 

 apparatus occurs anterior to the nucleus and immediately below 

 the bases of the two flagella. The basal bodies lie at an angle to 

 one another; in C. strobilus this is very obtuse, so that the kineto- 

 somes themselves are nearly parallel to the cell surface and 

 flagella emerge obliquely. No rhizoplasts or other root fibrils are 

 observed in most species, but in C. ericina fibrous connections 

 pass from lateral insertions on the kinetosome bases out to the 

 cell membrane or under the membrane to adjacent chloroplasts. 



In summary, a few morphological details may be noted that 

 seem to be consistent for the chrysomonads thus far investigated. 

 The chloroplasts generally are longitudinally oriented flanking 

 the nucleus, with lamellae running parallel to their long axes. The 

 two kinetosomes lie close but not parallel to one another. Free 

 flagella emerge generally at the level of the cell surface, or from a 

 relatively shallow depression. Rhizoplasts have been clearly seen 

 in three genera, and flagellum-stigma associations are found in 

 those species that posses stigmas. Golgi elements occur in a 

 specific and constant location near the basal bodies of the flagella, 

 but without evident physical linkage to these. Mitochondria are 

 microtubular. Thus far, all chrysomonads studied in any detail have 

 proved to be biflagellate, with the tentative exception of Hydrurus. 



