Young plants of S. ilicifolium and S. myricosystum appear in April and May and reach the maximum size in September or October. Alginic acid yield varies with the seasonal growth behaviour of these alginophytes. with maximum yield in July or August. Alginic acid content varies from 22.3 to 30.8% in S. ilieifolium and from 15.9 to 34.5% in S. myriocyslum. Mannitol content ranges from 2 to 5 and 1.3 to 5% in S. jlicifolium and S. myriocysmm respectively. The suitable harv.esting period for getting the maximum yidd of algin ic acid appears to be between July and September.