Abstract

• The plants of Hypnea spinella (C. Agardh) Kützing collected from the tidal pools in the upper intertidal zone of Setse coastal area (Lat. 15° 52' N, Long. 97° 35' E) had been culture under the laboratory conditions. It was carried out to investigate the formation and growth of H. spinella (C. Agardh) Kützing based on the early stages of secondary branches and reproductive structures in culture. In this study, the maximum growth was found in the salinity 25‰. After five days, a new filamentous sprout grew and seven days later, a single apical cell which develops at terminate of the branches and branchlets. After ten days, laterals and new branch filaments arised and after fifteen days initiating, short branchlets which gradually grow up on the branches like spiny outgrowth. Moreover, tetrasporangial form observed at the basal, middle and upper portion of the branchlets encircling the entire surface were described.