In oracle bone script and seal script, 兹 depicts two strands of twisted silk. It is the cognate of 丝. In clerical script, 艹 is added to express the meaning that the grass grows like strands of silk.
兹 serves as a phonetic component to form characters.
Characters formed by the phonetic component 兹
慈、磁、糍、甆、鹚 have the same pronunciation cí
滋、孳、 鎡、 镃、 稵、 嗞、 嵫、 禌 have the same pronunciation zī
See also the Component 丝
You can’t miss out the component 系 too.