Why is the cursive prefix in calligraphy written in two parts? What are the allusions?

We now call grass a grass prefix, in fact, the ancient Chinese characters in China are grass prefixes, as shown in the following figure.

Pictographs, representing two kinds of grass, were also written separately, and the two parts were not combined until later simplified Chinese characters.

This is a process of the evolution of Chinese characters, without allusions. In other words, this is culture.

In calligraphy, it is usually written alone, because it is varied and beautiful.