Hill. — A Revision of the Geophilous Species of Peperomia. 143 
into a short, irregularly tuberous rhizome ; and P. rupiceda , C. DC., a new 
species brought by Weberbauer from Peru, has also a short, more or 
less horizontal, tuberous rhizome some 2 cm. long, provided with adven- 
titious roots from all over the surface, and narrowed to the erect stem-apex. 
It is possible that P. puberula , Baker \ and some other species with 
well-developed rhizomes may also belong to the group, but until some- 
thing is known of the seedling structure it is best to omit them from this 
revision. 
The Leaves. 
The leaves in these geophilous species are peltate, except perhaps in 
the case of P. mexicana, though in this species the peltate nature of the 
lamina is well seen in the aerial cotyledon. The petiole is inserted in 
a median position, as in P. peruviana , P. campylotropa , and P. bracteata , or 
more commonly its insertion is at a point at about one-third of the length 
of the lamina from the base. In outline the lamina may be orbicular, as in 
two of the species just mentioned, or the apex may be more or less pointed, 
giving rise to an orbicular-ovate or ovate shape, as in P. bracteata , P. ovato- 
peltata , P. macrandra , &c. The lamina is usually flat, but in the small- 
leaved, xerophytic species of the parvifolia group it is slightly concave. 
There is a great difference in the texture of the lamina in the different 
species, and with this the character of the leaf venation is closely correlated. 
In P. peruviana the lamina is membranous when dry and the veins are 
very delicate ; in a transverse section only a single layer of palisade tissue is 
seen. Similar membranous leaves are found in P. ovato-peltata , claytonioides , 
macrandra , and gracillima , &c. Nothing is known of their internal struc- 
ture, but in these species it is evident from their appearance, and also from 
information supplied by the collectors, that they live in damp and shady 
places. A slightly stouter type of leaf, with a well-marked reticulate vena- 
tion, is found in P. timbilicata , R. and P., and in P. G audichaudii. The 
texture of the lamina in P. campylotropa , P. monticola , P. cyclaminoides , and 
P. rupiceda is of a still firmer nature, being somewhat coriaceous, and the 
radiating veins can be easily seen, but the internal structure is not known. 
The most highly specialized type of lamina is found in the parvifolia 
group, where it is very much reduced in size and increased in thickness. The 
small lamina is here usually orbicular-ovate or ovate, peltate about one-third 
of the distance from the base, and slightly concave. Of the three species 
concerned, P. parvifolia , P. verruculosa , and P. minuta , the internal structure 
of the leaf of the first two is known. In a transverse section two or three 
layers of palisade tissue are seen, below the water-storing tissue on the 
upper surface of the leaf, an arrangement correlated no doubt with the 
xerophytic conditions under which these species live. 
1 M. de Candolle tells me that lie now considers P. Mulleri and P. Botirgeaui to be the same 
species and identical with P. puberula , Baker. Cf. Hill, 1. c., p. 413 and footnote. 
