408 Hill. — The Morphology and Seedling Structure of the 
north-west of Mexico city. The ripe fruits are very similar in external 
appearance to those of P. parvifolia, C. DC., but they differ in the 
character of the pericarp and gland-cells and in the more pronounced 
stigma. They measure about 1-4 mm. in length by i-8 mm. in breadth, 
and the rounded seed is about -85 mm. by -8 mm. (Fig. 31, PI. XXX) 1 . 
The outermost layer of the fruit is composed of thick-walled elongated 
cells and covered with pits similar to, but rather more shallow than, those 
in P. parvifolia ; an important point of difference from this species is that 
only a single gland-cell occurs at the base of each pit. Below this outer 
layer the fruit-wall is seen, in a longitudinal section, to be only about three 
cells in breadth. <A single young seedling was found in the Herbarium at 
Kew which agrees exactly with the seedlings of P. peruviana, of the same 
age, already described (Fig. 30, PI. XXX). The relationship of the endo- 
sperm to the cotyledon and perisperm was, however, so well seen in this 
specimen, on dissecting away the seed, that a brief description is added. 
The endosperm fitted like the finger of a glove round the absorbent 
lamina of the young hypogeal cotyledon, and was attached to the seed-walls 
all round the apex of the seed, thus shutting off the perisperm from the 
cotyledon. On treatment with Iodine the contents of the perisperm cells 
become black-purple, but the endosperm tissue stains brown like the coty- 
ledon and only shows traces of starch, which gives a pinkish purple colour. 
From the somewhat club-shaped character of the absorbent cotyledon 
the seedling of this species seems to occupy an intermediate position 
between that of the seedlings of P. peruviana and P. parvifolia. 
In their later stages of development, the seedlings of P. umbilicata , H. B. 
and K., differ in an important and interesting manner from those of the 
South American species, and most, if not all of the other species belonging 
to the Central American and Mexican bulbous group show the same 
peculiarities. As a fairly complete series of the stages of germination and 
the development of the young bulbous plant of a Guatemalan species 
(P. pedicellata , Dahlst.) has been found, a description of these will suffice 
for the whole group. 
P. PEDICELLATA. 
In P. pedicellata , Dahlst. 2 , the fruits are borne on long pedicels, which 
are not quite equal to them in length (vide Fig. 32, PI. XXX). The fruit, 
including the stigma, is about 1-15 mm. long by -35 mm. broad, and is linear- 
obovate in shape, the stigma being -35 mm. in length ; the seed measures 
about -7 mm. by -3 mm. The fruit-wall is seen, in sections, to be of the same 
type as the pericarp in P. peruviana , Dahlst., having the outermost layer 
1 The figure given by Dahlstedt of the fruit of P. umbilicata, R. and P., PI. I, Fig. 8, appears 
to have been made from a Mexican specimen. 
2 Dahlst., 1 . c., p. 35, Pl. I, Fig. 13; T. D. Smith, Sta. Rosa, alt. 3,000 feet, No. 3829; 
O. Salvin, Volcan de Fuego, 6,400 feet, Guatemala. 
