A. xanthophloea, the famous Fever Tree with its pallid yellow bark, is apparently unique among the East African acacias in having flowers either white to pinkish or purplish, or else yellow to golden. White to purplish flowers are d for Kenya and Tanganyika (see, e.g., Bogdan, A List of Kenya Acacias with Keys for Identification: 1, 4 (1956) and T.T.C.L.: 334 (1949)), but nowhere, so far, south of these territories; while to the south of Tanganyika yellow to golden flowers are d by all collectors who mention flower-colour for A. xanthophloea. The only evidence for the yellow-flowered variant in our area is that the flowers of the type of the synonymous A. songwensis, collected perhaps in the same locality as Burtt 6040 (see above), are described as yellow; also that Semsei 2097, from Tanganyika, Pare District, near Same, is described as having bright yellow flowers. The geographical dividing line between the colour-variants is thus presumably in Tanganyika, but beyond that it is quite uncertain, presenting an interesting problem for observers in the field. I have so far failed to find any differences except colour between the two although closer observation may yet reveal them. White-flowered A. xanthophloea is closely akin to A. kirkii, especially subsp. mildbraedii, while the yellow-flowered form resembles A. seyal var. seyal. The differences are given in the keys. An apparent hybrid between A. seyal var. fistula and A. xanthophloea has been collected in Nyasaland (Greenway 6349) and crosses between the same two species should be looked for in East Africa.