With the objective to study the possible aqueous extract allelopathics effect of Cynodon dactvlon in the germination of cucumber (Cucumis sativus L.), com (Zea mays L.), bean (Phaseolus vulgaris L.) and tomato (Lycopersicon esculentum Miller). The extracts prepared from de shoot, moot and of the mixture root + shoot, had been triturated separately, in ratio 5ml of water: 1g plant material, filtered, centrifuged, being used the liquid floated. The aqueous extracts were added with distilled water in ratio 5ml of water : 1ml of extract. In the Petri dish with 10 seeds were put 10ml of dilute aqueous extracts for cucumber, 15ml for corn and bean and 5ml for tomato. The control was treated distiled water for each seeds type. The research was conducted in the ambient temperature. Moreover, to test the temperature effect in the extracts, une used the same treatments boiled, during five seconds. The results showed that the Cynodon dactylon different parts inhibited the tomato and cucumber seeds germination, but did not inhibited the corn and bean seeds germination. Therfore it was possible to conclude that the Cynodon dactylon synthetized substances had the allelopathic action on the cucumber and tomato seeds germination.