whisk ferns; comprising the family Psilotaceae or Psilotatae: vascular plants with no roots,partial if any leaf differentiation,and rudimentary spore sacs

• 蕨类植物；由松叶蕨科或裸蕨纲组成；无根脉管植物，叶仅部分分化或缺乏，孢子囊发育较差