The variations in East Africa of A. sieberiana seem to fall into two groups, var. sieberiana in one and vars. vermoesenii and woodii in the other. Mr. C. G. Trapnell writes (in litt.) of “the characteristic mushroom-shaped crown [of var. vermoesenii ], of great width in proportion to the length of bole, which contrasts sharply in the field with the ascendent branching of A. sieberiana. Var. vermoesenii in west Uganda occupies higher rainfall areas and higher altitudes than the main species, the dividing line in the region in which we were working answering to about the 36 ins. isohyet.” As far as can be ascertained the habit and ecology of var. woodii are decidedly those of var. vermoesenii and not var. sieberiana. At present vars. vermoesenii and woodii do not appear to share any common distinctive characters other than those mentioned in the descriptions above, except tendencies to produce more pinnae and wider pods than in var. sieberiana; thus the pods of var. sieberiana are up to about 2.5 cm. wide (rarely, as in Greenway 9103, from Tanganyika, Masai District, Seronera NE. to Naabi Hill, 2.2–3.2 cm. wide), while those of the other two varieties are often up to 3 and sometimes to 3.5 cm.; there is however much overlapping. Careful field-work is greatly needed in various parts of the range of A. sieberiana, which may show that the two groups mentioned in the first sentence are subspecies or even species; if the latter, then A. nefasia is the correct specific name for that group comprising vermoesenii and woodii. At present it seems more prudent to maintain the three recognized varieties, especially because they are all connected by intermediates. These are particularly frequent between vars. vermoesenii and woodii, and it is hard to refer them either to one or the other. Examples are Tanganyika, Mpanda District, Kabungu, Semsei 59 in F.H. 2491!, Mpwapwa District, Mpwapwa, Hornby 735! & Kiboriani Mts., Hornby 944!, Mbeya District, Mbozi, Jessel 67! Intermediates between var. sieberiana and var. vermoesenii are shown by Michelmore 1308! and Trapnell 2188! both from Mbirizi in Masaka District, Uganda. Wigg 16!, referred to A. woodii in T.T.C.L.: 335 (1949), is I think better placed under var. vermoesenii.
