The Vigant Cave (110/66 Fr), shows an extremely various and interesting speleological and vegetation environment. Both the area before the mouth and the first part of the entrance, although situated at a relatively low level (540 m), include a consistent group of species mainly marked by Pre-Alpine or Continental-Alpine characteristics. The presence of this exuberant cave-dwelling kind of vegetation is strictly related to the cave topo-climatic dependence and, in a particular way to the majestic access portal exposition that turns westwards that can be found at the blind flyschoidal eocenic pit end in which flows the Tanaloho (or Tapotcletia) brook. Very luxuriant and assorted is, within the cave complex, the floristic composition that is already present at the beginning of the spring season; therefore, one after the other, several various entities blossom during the summer season to end, with further other species, in the autumn season. Among all, the vegetation elements that blossom in the Vigant complex, some have a particular and remarkable botanic value: first among all of them, the rare Matteuccia struthiopteris (ostrich-feathered fern, see picture), Pteridofyta of extraordinary elegance and beauty that here finds, as far as we are currently aware, its lowest regional level. An ample and detailed dissertation is devoted to this Onocleacea in the prosecution of the present contribution. Of remarkable relevance, here also appear the presences of alpine Arabis, Saxifraga petraea, camiolic Euphorbia and green Asplenium. Also these species underline, in the particular hyogeal environment examined, some of the most southern presences of their regional distribution.