‘Stalagmiform’ roots are here defined as dense, stalagmite-like aggregations of roots and rootlets which protrude from the sandy floor of certain limestone caves. Paper chromatography showed these structures were associated with large trees of Eucalyptus gomphocephala growing above the caves. They seem to form in response to localized abundance of water at sites beneath drip-points in the cave ceiling.
The anatomy of ectomycorrhizal and non-infected stalagmiform rootlets was similar to that of Eucalypt rootlets. Non-pathogenic endophytes were also often present, giving many rootlets an endomycorrhizal character. This unusual combination of features places the stalagmiform root in a separate category from other specialized root structures.