Several leaf blades of the cultured Isoetes sinensis from tender to mature are used as experimental materials in this paper.With the method of paraffin technology,the development of ligule and velum are observed by continuous dissection.The relationship between the development process and the sporangium and blade are analyzed.The results show that:(1)The primeval developing speed of the ligule was faster than that of the leaf blade,although the ligule and leaf blade come from the same primordia in the early ontogenesis of I.sinensis.(2)Sporangium first occured at the fifteenth blade stage of I.sinensis,when the velum was obvious in the bottom of ligule.(3)When the antiphyte of I.sinensis achieve more than 30 pieces of blades,the sporangium that produced in plant peripheral in early time has been matured.In this period,the megasporangium and the microsporangium can be divided clearly and the length of ligule that relative to sporangium has become short in mature macrosporophyll.The labium is atrophied and the velum has disappeared;Compared with the macrosporophyll,the ligule of mature microsporophyll is longer and upturned extent is obvious.The atrophied degree of the labium is unconspicuous and the velum has disappeared.The studies suggest that the velum was a common structure in the early phylogeny stage of Isoetale,but significant degradation or even disappear in later stage of evolution at some areas;the difference between ligule and leaf blade was less obvious than that of morden isoetale,when I.sinensis was in the early phylogeny.