Co-text is different from context. It is a internal aspect of text. But context is a external aspect of text. Generally co-text is called as a text-flow. It is very abstract concept. It has been ambiguously treated with at scene of school. Co-text may be kind of rhythm in text. Especially it distributes the whole range of text. Between the words, sentences, paragraphs, and rhetoric unit are distributed. So the range is not easily decided. The problems cause the understanding difficulties of text. This paper is focused to concrete abstract co-text. Two methods are used in actualization. First, cognition and representation in linear relation of text are treated by Centering theory. Centering theory is about the cohesion. Especially it is about how pronoun is restored between sentences. Also the representation is exposed by the rectangular coordinate system. Second, tree-diagram is used to exposed hierarchial relation between paragraphs. This method actualizes cognition and representation in hierarchial relation of text. So the co-text is represented by horizontal and vertical relation.