336 
LIIL—ACANTHUS PUBESCENS AND A. ARBOREUS. 
iC ORRILE: 
The Tropical African Acanthaceae were worked out by the late 
Mr. C. B. Clarke and published in the Flora of Tropical Africa in 
1899-1900. On p. 106 of vol. v. of this work he describes 
Acanthus arboreus, Forskal, and reduces as synonymous with it the 
species A. polystachyus, Delile, A, oe nie Engler, and A. Gaéd, 
Lindau, and the variety pubescens, T. Thoms., of A. arboreus. ie 
naming the Acanthaceae of the Kissner Expedition, 1908, it was 
found that a revision of the synonyms given under and of the 
characters given for A. arboreus, Forsk., in the flora was necessary. 
The results of the investigation are recorded below. 
The degree of hairiness in A. pubescens, Eingl., and the allied 
species is not to be relied upon as a specific or even varietal 
character, but characters which are constant and in accordance with 
geographical distribution are to be found in the sepals. Before 
giving the results obtained by the use of these characters it will 
be well to give a brief oe resumé of the species and their 
synonyms under discussion. arboreus was described by Forskal 
from specimens collected in ibis. The description is meagre but 
sufficient to show that A. pubescens, Engl., was not the plant meant. 
The name A. arboreus is the name “generally accepted for the 
Abyssinian and Somaliland plant as well as for the Arabian plant. 
At Kew there is only one specimen (Schweinfurth 1112) collected in 
Arabia and this has only an imperfect calyx. If, however, the 
Arabian and Abyssinian plants prove to be different the latter must 
ear the name A. polystachyus, Delile, and the name A. arboreus, 
Forsk., must be retained for t ie former. Thanks to the eo) 
< form of A, ie eus, Pon , has been described by Lindau from 
Somaliland as A. Gaéd. The type specimen, Hildebrandt 1399, is 
at Kew and appears to differ from typical A. arboreus, Forsk., only 
in having smaller flowers. Acanthus arboreus, Forsk., var. pucbeseehs 
is first used (as a nomen nudum) in Speke’s Nile J ourney, pe 
p- 643. It was shortly described by Oliver in Trans . Soc., 
vol, xxix., p. 129. The specimen on which this font was 
founded, namely, Speke and Grant 136, must be taken as the type 
of , pubescens, Engler, though that author included under the one 
name two other specimens one of which, Steudner 1532, is merely a 
pubescent form of A. arboreus, Forsk., while the other is not repre- 
sented at Kew and has not been seen by the writer. 
To A. pubescens, Engler, be referred A. ugandensis, 
C. B. Clarke, publishe d in ne Fe ournal of the Linnean Society, 
vol. xxxvii., p. 527, ae including specimens collected by Dawe and 
Evan James in Ugand a, and by C. F. Elliott in British East 
Africa. hee German I egether | with the material from Uganda 
erman 
