Asplenium listeri Asplenium listeri Asplenium listeri, commonly known as the Christmas Island spleenwort, is a species of fern in the Aspleniaceae family. It is endemic to Christmas Island, an Australian territory in the north-eastern Indian Ocean. Its specific epithet honours British zoologist and plant collector Joseph Jackson Lister, who visited the island on in 1887 and was the first to collect a specimen. The spleenwort is a small, terrestrial, lithophytic fern with shortly creeping rhizomes, and with fronds up to 90 mm long held in a crown. Found only on Christmas Island, the fern is known from a very small number of
Plant cell quite elongated, and may divide transversely to give a septate appearance. The role of this cell type is to support the plant in axes still growing in length, and to confer flexibility and tensile strength on tissues. The primary wall lacks lignin that would make it tough and rigid, so this cell type provides what could be called plastic support – support that can hold a young stem or petiole into the air, but in cells that can be stretched as the cells around them elongate. Stretchable support (without elastic snap-back) is a good way to describe what collenchyma does.