 B. telmatiaea is one of five Banksia species , all closely related to B. sphaerocarpa , that have highly unusual flower nectar . Whereas other Banksia species produce nectar that is clear and watery , the nectar of these species is pale yellow initially , but gradually becomes darker and thicker , changing to a thick , olive @-@ green mucilage within one to two days of secretion . In the case of B. telmatiaea , it eventually becomes " an almost black , gelatinous lump adhering to the base of the flowers " . This unusual nectar was first noted in 1980 by Byron Lamont , who attributed its transformation to the cyanobacteria that he observed feeding off the nectar sugars . Noting that many of these cyanobacteria had heterocysts , he speculated that they aid the plant by fixing atmospheric nitrogen , which is then washed off the flower heads by rain , and absorbed by the proteoid root mat . This purported symbiosis was investigated in 1985 , but no evidence of nitrogen fixing was found . Further investigations in 1996 suggested that the discolouration is not caused by cyanobacteria or other microorganisms in the nectar , but is rather " a chemical phenomenon of plant origin " . As of February 2007 , the cause was still unknown . Chemical analysis of B. telmatiaea nectar has shown it to have a normal nectar sugar composition , albeit dominated by sucrose . 
