Summary.Studies on clones ofcynodon dactylon(L.) Pers. have revealed the existence of four biotypes of this species. The sole use of morphological characters to classify them was found unsatisfactory and other definite diagnostic characters have been introduced comprising hair group characteristics and leaf and stolon epidermal structures. Cytotogical studies showed that the biotypes differ in their chromosome number; tetraploid and triploid races have been distinguished. Phasic growth investigations have pointed out that thr biotypes have a similar growth behaviour but that the tetraploids are more vigorous plants than the triploids. Studies on the seasonal variation in available carbohydrates in rhizomes and roots have established that the seasonal trend of this reserve substance in these organs is related to rhizome growth.Recherches sur des biotypes deCynodon dactylon (L.) Pers.