294 ROBINSON. 
but not always much uiore acute at tlie base, the apex is mueh more gradually 
contracted into the very distinctly longer acumen, the margins differ as the two 
original descriptions indicate, and the creuations of /'. crassifoJia are propor- 
tionally deeper, and the lateral nerves somewhat nearer the margin in that species. 
Tlie most conspicuous difference is in the color of the dried leaves, which are 
darker on both surfaces of the Boniean plant, the under surface being brown or 
by means of the cystoliths somewhat golden-brown, the nerves nearly the same 
as the rest, whereas in P. intiimescenfi the under surface is glaucescent, the 
nerves the same or Mith a reddish-brown tinge. It is possible that fuller collec- 
tions might unite these two species, but on the material at present available 
they seem to be sufficiently distinct. P. .pterocaulis has also much the appearance 
of P. rohinsotiii Elmer, but is much smaller, the leaf-margins are different, and 
the foruicr is trinerved and the latter triplinerved. 
Pilea johniana Stapf 1. c. 227, pi XIX, fg. T), 11-^6. 
Ivinubiilu, Ilaviland 1391, type collection. P, liumiUs C. B. Eob. differs dis- 
tinctly by the larger, thinner, less crowded leaves. 
Pilea rigidiuscula sp. nov. 
Suffimtex (?)j glaber: inflorescentiis pistilliferis quam petioli breves 
brevioribus; perianthii lobis 3, lateralibus quam intermedius multo 
niinoribus: petiolis oppositiSj saepissime imo quam alter sesquilongo, 
rarius conspicue inaequilongis vel aequilongis^ laminis rigidiuscule cliar- 
taceis, anguste ellipticis vel lanceolatis, basi angustatis obtusis retusisque 
rarissime acutis, margine supra quintam basalem partem leviter dentatis, 
apice acauiiinatis, saepissime triplinerviis ; stipulis parvis, orbiculari- 
triangularibuSj caducis. 
Pistillate inflorescences 3.5 mm long or less, the peduncles very short 
or practically none, very sparingly branched, few-flowered ; pedicels very 
short : perianth-lobes 3, the intermediate oblong-lanceolate, 0.5 to 0.6 mm 
long, the laterals broadly ovate, about 0.3 mm long; achenes compressed- 
ovoid, more or less oblique, 0.8 mm long, papillose toward the margins. 
From the material probably a low, branching undershrub; leaves op- 
posite, the petiole, of one of a pair more often about one and one half 
times the length of that of the opposed leaf, sometimes very unequal or 
almost exactly. equal, 2.5 to 25 mm long, the lamina rigidly chartaceous, 
narrowly elliptic to lanceolate, 3 to 6.5 cm long, 1 to 2 cm wide^ almost 
equilateral except sometimes at the extreme base, tlie base narrowed, 
obtuse and retuse or rarely acute, the margins except toward the base 
shalloAvly dentate, the apex forming an acumen similarly dentate about 
6 to 8 mm long; usually definitely triplinerved, or the lateral nerves 
approaching the costa near the base and one or both continued to the 
petiole, or veiy rarely trinerved, the veins connecting the lateral nerves 
witli tlie costa slender, about 10 in number but often connected with a 
slender intermediate nerve, the lateral nen^es continuous to the base of 
the acumen; upper surface of lamina duU-greon with greatly crowded 
conspicuous cystoliths, under surface much paler, with equally crowded 
