fern ally - pteridophytes of other classes than Filicopsidawhisk fern - chiefly tropical clump-forming plants of skeletal appearance resembling whisk brooms; lacking roots horsetail - perennial rushlike flowerless herbs with jointed hollow stems and narrow toothlike leaves that spread by creeping rhizomes; tend to become weedy; common in northern hemisphere; some in Africa and South America quillwort - any of several spore-bearing aquatic or marsh plants having short rhizomes and leaves resembling quills; worldwide except Polynesia |