Geopkilous Species of Peperomia . 409 
composed of tangentially elongated cells with single gland-cells inter- 
spersed (Fig. 41, PI. XXX). 
In the youngest seedling stages discovered, the aerial cotyledon is 
fully expanded ; its lamina is rotund-cordate to ovate more or less acute, 
about 3-5 mm. long and 2*5 mm. broad, trinerved and very slightly peltate, 
the insertion of the petiole being almost at the base. The hypogeal 
cotyledon, as in the other cases, remains embedded in the seed, and the 
petioles of the two cotyledons spring from a small, slightly swollen 
hypocotyl, which is prolonged into the short primary root or radicle (Fig. 33, 
PL XXX). On dissecting away the fruit and seed the included, absorbent 
lamina is found to be oblong in shape, -6 to *7 mm. in length, obtuse and 
slightly concave, with a single median vascular bundle (Fig. 34). Near 
the middle, and apparently on the lower side of this cotyledon, a single 
stoma was found in one case, with starch in the guard-cells ; whilst in 
another case three stomata were found at the apex of the cotyledon, but there 
was no indication of starch. These latter stomata may perhaps be of the 
nature of water-stomata. Slightly older seedlings show further stages in 
the development of the tuber ; the primary root, which at first is in a 
straight line with the hypocotyl and plumular dome, becomes laterally 
displaced, owing to the growth of the tuber taking place mainly on one 
side. At about the same time a lateral root is given off from the base of 
the primary root, and this at first grows upwards, but then bending over, 
keeps a more or less horizontal course at about the level of the top of the 
tuber (Figs. 33 and 35). 
The unilateral development of the tuber continues, with the result that 
the point of insertion of the primary root is gradually carried round until 
finally the root or tuft of young roots comes to spring from what is now 
the upper surface of the bulb (Figs. 35-38). The point of origin of the 
roots thus lies to one side of the shoot-apex on the physiologically upper 
surface of the tuber, so that these points are separated from one another by 
only a small intervening space, which represents one of the sides of the 
hypocotyl of the young seedling. The small spherical bulb or tuber is 
a true corm, as in the South American species, but, owing to this curious 
asymmetrical development, it has assumed the appearance of a root tuber, 
such as one finds in Ranunculus ficaria. When the primary root has been 
brought round to the upper surface of the tuber in the manner just 
described, it becomes replaced by numerous lateral roots, which spring 
from its base ; these then grow out all round over the top of the bulb in 
the horizontal direction, and pass on either side of the shoot with its 
leaves. The roots are thickly covered with root-hairs and do not branch 
very freely, but they all spring very definitely from one spot (Figs. 38 and 
39). In an old tuber an occasional root can be found arising a little away 
from this spot. 
