In 1968

Aristid Lindenmayer introduced a formalism for simulating the development of plant

subsequently named L systems. This formalism was closely related to abstract automata and formal languages. But there is a shortage in programming by the L system codes to construct plants graphic .The shortage is it's complicate and the low productive in its code because the program has to reuse the same code and traverse or modify the same linked list's each node to draw the plant graphic in every status. To make up this defect

this paper analyses and testifys a quality that those L system creating graphics in different status are of fractal character. Furthermore

the paper advances an improvement method based on this quality

which means that generation of the plant graphic in the later status can directly make use of the plant graphic in the former status. In other words

the later status graphic only is the former status graphic's enlargement?translation and revolving. Concretely

the new method is let the L system code into a simple recursion expression which can make the program code cut down and bring up the speed of draw a plant's graphic. A example of the new method is given at the end of the paper. So we can acquire a very useful conclusion in simulating plant with the L system theory which turn the L system code into a recursion expression.