HilL — A Revision of the Geophilous Species of Peperomia. 141 
to this confusion that the classification of the geophilous Peperomias has been 
so difficult, and it was in the hope of arriving at a solution of the problem 
that this research was undertaken. 
General Morphology. 
The correlation between the pseudo-monocotyledonous method of 
germination and the geophilous habit in these Peperomias has already been 
discussed x , and some account of the underground tuberous portion of 
these plants has been given, but it will be useful to refer briefly to the 
various types of bulb or rhizome which are found among these species at 
this point, on account of their value for purposes of classification. 
There appear to be four well-marked types of underground stem, 
which will be distinguished by the names of the prominent species. 
In the simplest or parvifolia type there is a simple, smooth, more or 
less spherical corm, with a basal tuft of roots and an apical crown of leaves 2 . 
In the case of old corms, owing to the division of the growing-point, there 
may be two or three rosettes of leaves. The central cylinder runs vertically 
through the corm from the stem-apex to the point of emergence of the roots, 
and the general appearance and structure very closely resembles that of 
a crocus corm. To this type belong four Peruvian and Bolivian species, 
P. parvifolia , P. verruculosa , P. minnta , and P. cyclaminoides . 
To the next or umhilicata type belong those species in which the 
underground stem is a hypocotyledonary tuber, as in the preceding group, 
but the roots arise irregularly from the sides and base 3 . In the seedling 4 the 
primary root is vertical, but it is soon replaced by adventitious roots which 
spring from the sides of the little tubers 5 . The three species from South 
America, which must be included here, differ somewhat from each other. 
In P. umbilicata , R. and P., collected by Pavon, the roots arise in a some- 
what regular ring round the middle of the spherical tuber, leaving the 
upper part free, and having a few roots scattered over the base ; whilst in 
P. peruviana and P. falsa the roots are scattered in an indefinite manner 
over the sides and base of the tuber, which is often warted and irregular in 
outline G . 
The third or campylotropa type is of particular interest, and an account, 
with figures of the development of this peculiar form of tuber, has been 
given in the previous paper 7 . Some nine or ten species belong to this 
group and, with one exception, are all natives of Mexico and Central 
America. In the paper referred to, the opinion was expressed that this 
form of tuber was entirely confined to the Mexican region, but from an 
1 Hill, 1. c., p. 397. 
3 Cf. Hill, 1. c., PI. XXIX, Figs, i and 2. 
5 1. c., PI. XXIX, Figs. 11 and 15. 
7 1. c., pp. 407-410, PI. XXX, Figs. 532-39. 
M % 
2 Cf. Hill, 1. c., PI. XXIX, Fig. 27. 
4 1. c., PI. XXIX, Figs. 5-10. 
6 1. c., PI. XXIX, Fig. 1. 
