Chlorella spp. endosymbionts of the foraminifera Amphistegina lessonii and Amphisorus hemprichii were axenically cultured in screw-capped tubes and tested for vitamin effects on growth which was enhanced by 380-400%. Culture tubes were grown in a thermal gradient incubator ranging from 15-40.degree. C. Both algal species survived 15-38.degree. C and grew between 22-33.degree. C while optimal growth was at 28.5.degree. C. The release of metabolites by the 2 Chlorella spp. was tested. The chlorophytes released less than 1% of the total C fixed to the growth medium. Glucose and mannose were identified by TLC of the growth medium.