Krinzlin in Engler Pflanzenr. LV. 50, pt. 2 (Heft 80) 
(1922) 301. 
Petalocentrum Schlechter in Fedde Repert. 15 (1918) 
144;  Kranzlin in Engler Pflanzenr. [V. 50, pt. 2 
(Heft 80) (1922) 312. 
The concept Petalocentrum was separated from the 
variable genus Sigmatostaliv by reason of three alleged 
differences (Cf. Schlechter in Fedde Repert. 15 (1918) 
145), viz. the sessile lip, the spur-like outgrowth at the 
base of the petals and the ascending rostellum. 
The characterization of the lip in the type description 
of Sigmatostalix (1.c), to be sure, specifies ‘‘labellum un- 
guiculatum.’’ However, the lip in the typical species, 
S. graminea (as Specklinia graminea Poepp. & Endl. in 
Nov. Gen. ac Sp. 1 (1836) 51, t. 89 B), appears to be 
cuneate below to a sessile base; and, even if the analysis 
is discarded as being inadequate (on the basis of later 
representations), that organ seems to be at most only 
very shortly unguiculate. 
At any rate, some species which were described as be- 
longing to Sigmatostalivx, such as the Central American 
S. hymenantha Schitr., have the basal part of the lip 
more or less cuneate to a sessile base (apparently very 
broadly cuneate). And other species, such as S. macro- 
bulbon Kriinzl., have an absolutely sessile lip. In the face 
of such wide variation, therefore, it seems advisable to 
discard this character, at least as to its generic value. 
As regards the spur-like outgrowth on the petals, this 
character appears to be quite absent in some species with 
a strikingly sessile lip which were referred to Sigmato- 
stalix, such as iS. macrobulbon Krinzl. Nor does this 
character appear in S. hymenantha Schltr. with the 
broadly cuneate base to the lip. It would seem, there- 
fore, that this outgrowth on the petals, seen in one poly- 
