Some Observations on the Fine Structure of Vegetative and Dividing Cells of Chlorococcum Echinozygotum Starr1

SUMMARY Chlorococcum echinozygotum Starr was grown in a modified Bristol's solution, and in the same medium in which strontium had been substituted for calcium. After 3 and 6 weeks growth, cells were transferred to fresh Bristol's solution overnight to initiate motile cell production. Dividing cells were fixed in 2.0% K permanganate, and embedded in Epon. The ultra‐structure of several stages in the life history of the organism is described. Light and electron microscopic observations indicate that progressive cleavage of the protoplast occurs, as well as the previously reported successive bipartitioning. A Sr replacement for Ca in the growth medium apparently has no demonstrable effects on the development of cell organelles in C. echinozygotum. Many investigators have contributed to our understanding of the ultrastructure of the algae (1,4,5,6,7, 8,15,16). Studies of vascular plants (9,19) and algae (11,12,13) indicate that cells and cell organelles do not develop normally when some elements are lacking. This study reports observations on the ultra‐structure of several stages in the life history of the alga, C.hlorococcum echinozygotum Starr, which was grown in a modified Bristol's solution (3) and in the same medium with strontium substituted for calcium.