Mycorrhizae in Adenostoma fasciculatum Hook. & Arn.: a combination of unusual ecto- and endo-forms

The mycorrhizal status of Adenostoma fasciculatum, the dominant shrub in Ca lifornia chaparral, has been unclear. In two typical, nearly monospecific s tands, A. fasciculatum was found to have arbuscules and intercellular hypha e. Antisera detected hyphae of the arbuscular mycorrhizal (AM) fungal gener a Acaulospora, Glomus, and Scutellospora, although we found only spores of Glomus. Some roots had partial sheaths and inter- and intracellular septate fungi without indications of root necrosis. Ectomycorrhizal root tips were also found, including Cenococcum and other unknown taxa. Sporocarps of EM fungi including species of Rhizopogon, Pisolithus, Balsamia, Laccaria, Hygr ophorus, and Cortinarius were found in the stand, with no other EM or arbut oid mycorrhizal plants nearby. These observations indicate that A. fascicul atum forms mycorrhizae with AM, septate, and EM fungi, but often fails to f orm easily recognizable mycorrhizal structures.