SUMMARYThe anatomical structure of different plant organs of nearly all the species of the eight genera of the Xanthorrhoeaceae has been described. The xylem elements of representative species of all the genera have been investigated in macerated material. True vessels have been found in the roots of all the genera, and in the leaves ofXanthorrhoeaandAcantho‐carpus.No tracheal elements except tracheids have been seen in the leaves of the other genera, or in the stems or rhizomes of all the genera. When these data are compared with those established by Cheadle (1942) for other families of the monocotyledons, it will be seen that the Xanthorrhoeaceae most closely resemble the Agavaceae. Amphivasal vascular bundles occur in the stems and/or rhizomes of all the genera exceptKingiawhere the xylem in all the bundles is U‐shaped in transverse section. The stem structure ofXanthorrhoeaprovides evidence that the amphivasal type structure has arisen by the fusion of pairs of bundles with U‐shaped xylem. The leaves of all the genera have a xero‐morphic anatomical structure. Special arrangements and structures, which prevent excessive evaporation occur in the stomatal regions inXanthorrhoea, KingiaandBaxteria.A special type of palisade cell with annular contractions, and/or with papillose projections, occurs inKingia, Calectasia, Lomandraand to a lesser extent inDasypogon, and traces of this type of structure are also to be seen in the other genera of the