1.  helmet orchid(n = noun.plant) greenhood - any of numerous orchids of the genus Pterostylis having leaves in a basal rosette and green flowers often striped purple or brown or red with the dorsal sepal incurved to form a hood;
is a kind of orchid, orchidaceous plant
is a member of genus pterostylis, pterostylis

2.  helmet orchid(n = noun.plant) helmetflower - any of several orchids of the genus Coryanthes having racemes of a few musky-scented waxy flowers with a helmet-shaped lip process;
is a kind of orchid, orchidaceous plant
is a member of coryanthes, genus coryanthes

alaska rein orchid, balaclava helmet, batting helmet, bee orchid, blue orchid, bog rein orchid, butterfly orchid, coastal rein orchid, common spotted orchid, crash helmet, dancing lady orchid, early purple orchid, early spider orchid, fen orchid, fly orchid, football helmet, foxtail orchid, fragrant orchid, fringed orchid, frog orchid, funnel-crest rosebud orchid, gas helmet, greater butterfly orchid, helmet, helmet flower, hooker's orchid, jewel orchid, jumping orchid, lesser butterfly orchid, lizard orchid, marsh orchid, moth orchid, orange-blossom orchid, orchid, orchid cactus, orchid family, orchid tree, pansy orchid, phantom orchid, pith helmet, poor man's orchid, prairie orchid, prairie white-fringed orchid, purple fringeless orchid, purple-fringed orchid, ragged orchid, ragged-fringed orchid, rattlesnake orchid, rein orchid, rosebud orchid, round-leaved rein orchid, satyr orchid, short-spurred fragrant orchid, slipper orchid, snow orchid, snowy orchid, space helmet, spider orchid, stream orchid, sun helmet, swan orchid, tangle orchid, tulip orchid, vanilla orchid, water orchid, white fringed orchid, zebra orchid