Acroceras.] 
CL VII. GRAMINEiE (Stapf). 
627 
lanceolate to lanceolate-oblong, 3-nerved, middle-nerve suddenly 
widened towards the tip into an acutely ending keel ; upper as 
long as the spikelet, oblong, acuminate, 5-nerved, apiculus laterally 
compressed, oblong, obtuse, very minutely scaberulous. Lower 
floret barren : valve very similar to upper glume ; valvule linear, 
almost as long as or distinctly shorter than the valve, subacute, with 
scaberulous keels. Upper floret Q linear to linear-oblong, bluntly 
apiculate, 2J lin. by slightly over \ lin., whitish, smooth : valve 
and valvule coriaceous, apiculus of valve short, obtuse, of valvule 
slightly recurved and subacute or 2-toothed ; anthers 1 \ lin. long. 
Lower Guinea. Belgian Congo : Stanley Pool Distr. ; Kitebe, Vanderyst, 3642 ! 
4118 ! 4144 ! 4145 ! between Leopoldville and Mombaxi, Gillet, 2619 ! 2704 ! 
68b. COMMELINIDIUM, Stapf. 
Spikelets oblong, subobtuse, subterete, falling entire (or sub- 
entire ?) from the pedicels, usually 2-nate or solitary, more rarely 
fascicled, subsecund and abaxial on the angular rhachis of racemously 
arranged loosely or interruptedly spicif orm racemes ; lower floret 
barren with a more or less reduced valvule ; upper floret Glumes 
similar in texture, membranous, greenish, with slightly callous 
tips ; lower shorter, ovate from a clasping base, 3-nerved ; upper 
oblong, broadly rounded on the back, 5-nerved, separated from 
the lower by a distinct internode. Lower floret equalling upper 
glume : valve very similar to upper glume ; valvule much shorter 
than the valve, hyaline, with narrowly winged keels and upwards 
evanescent flaps. Upper floret : valve oblong-lanceolate, broadly 
involute with firm margins, minutely cucullate, with a small 
blunt apiculus, coriaceous, smooth with a dorsal semilunar de- 
pression at the base ; valvule almost equalling the valve and similar 
in substance, with rounded keels and an entire tip, embraced 
by the valvule ail along or the very tip free. Lodicules 2, cuneate, 
fleshy. Stamens 3. Styles distinct, plumose, purplish, exserted 
laterally towards the tip of the spikelet. Grain unknown. — Perennial 
from a prostrate rooting base, with much the habit of certain broad- 
leaved Commelince or of Polys'paiha ; blades obliquely ovate, 
contracted at the base and articulated with the sheath, many- 
nerved with transverse veins ; ligules distinct, membranous ; 
panicles of rather few branches, bearing spikelets from low down ; 
spikelets quite glabrous and smooth, except at the mostly minutely 
puberulous tips. 
Species 3, endemic in West Africa. 
My observations on the affinity of Acroceras (see above) may be applied with 
even greater force to Comm,elinidium, which should have been placed between 
Chloachne and Microcalamus. The curious dorsal semilunar depression at the 
base of the fertile valve corresponds to a very considerable reduction of tissues, 
and in the mature state frequently leads to a rupture along its line. The portion 
of the valve immediately inside the line bulges slightly. The same structure 
