A Review of the Genera Erythrococca and 
Micrococca. 
BY 
D. PRAIN, C.I.E., F.R.S. 
Director of the Royal Gardens, Kew. 
Introductory. 
I N a paper ‘ Sur le Mercurialis alteniifolia , Desr., et sur les limites du 
genre Mercurialis 5 (Adansonia, iii. 167-76) Baillon, in 1862, essayed to 
prove that Lamarck’s treatment of this plant, 1 on which Bentham based the 
genus Micrococca (Hook., Niger Flor., 503), is valid, and that, as a consequence, 
the genera Adenocline, Turcz. (Bull. Soc. Imp. Nat. Mosc. 1843, 59), Seidelia , 
Baill. (feud. gen. Euphorb.,465,t. 9), Claoxylon, A. Juss. (Tent. Gen. Euphorb., 
43, t. 14) and Erythrococca , Benth. (Hook., Niger Elor., 506) are also referable 
to Mercurialis. These Euphorbiaceous types undoubtedly belong to a 
definite natural group, and our instinctive reluctance, even when the necessity 
is more obvious than in this case, to include in one genus annual herbs like 
Micrococca , Adenocline , Seidelia, and shrubs or trees like Claoxylon and 
Erythrococca is shaken by the logic of Baillon, who shows that characters 
based on the number and arrangement of the stamens and of the glands on 
the receptacle so usually associated with the stamens in this assemblage of 
types are not of generic significance. Were these the only differential 
characters available here, Baillon’s conclusion is hardly to be questioned. 
But while all that Baillon urges with regard to the relative characters 
afforded by the androecium may be admitted, his reasoning involves an 
assumption that certain differences in the stamens themselves are unim¬ 
portant. This assumption does not affect the existence of these differences ; 
the fact that they exist leaves room for another opinion. 
In the species referable to Mercurialis, Linn., in the usual restricted sense, 
the anther cells at first are pendulous or divaricate. In all those types which 
1 Lamarck, Encyc. Meth., iv. 120 (1796); the plant had already been dealt with by Linnaeus in 
1 753 (Sp. PL, 980) as a Tragia ( T. Mercurialis'). Baillon attributes the name M. alternifolia to 
Desrousseaux, but the authorship of the article Mercurialis is not credited by Lamarck, in the text, 
to that botanist. Mueller (DC. Prodr., xv. 2, 790) is certainly under a misapprehension in attributing 
the name to Desvaux. 
[Annals of Botany, Vol. XXV. No. XCIX. July, 1911.] 
Q q 2 
