Robuta

https://kuscholarworks.ku.edu/entities/publication/ecf30f20-7c5e-4f00-81bb-debe1b8350af Phloem anatomy of the Carboniferous pteridosperm Medullosa and evolutionary trends in gymnosperm... Secondary phloem anatomy is detailed for four species of Medullosa from various coal ball localities in North America, ranging from Lower-Middle to Upper... of the