Aug. 5, 19x3 
Anatomy of the Potato Plant 
225 
to the margin of the leaves a greater density than has the inner part of the 
lamina. 
Young potato leaves are densely clothed with hairs, some of which are 
long and straight, others short and of the glandular type. The straight 
hairs are either one or several celled. The glandular hairs have a spherical 
head, usually four-celled and borne upon a slender, short pedicel. The 
mature leaf, however, is only sparingly covered with hairs, and these 
arise mainly from the midrib and the lateral veins. Stomata are found 
on both surfaces, but are more abundant on the lower. 
The inflorescence is a monochasial cyme. The peduncle, though lat¬ 
eral, occupies a central position, having become stronger in its develop¬ 
ment than the stem tip, pushing aside the latter, which comes to occupy 
a position apparently lateral. The flowers are 5-merous and are borne 
on bractless pedicels. The gamopetalous corolla is tubular, with five 
lobes which are white, yellow, purple, or blue in color. The calyx is 
also tubular and 5-lobed. There is a single whorl of five stamens alter¬ 
nating with the corolla lobes and attached to the tube. The stamens are 
straight or slightly curved, with yellow anthers which are longer than 
the filaments, and converge around the style, each opening by two pores 
at the top. There are two completely fused carpels, forming a 2-celled 
ovary with a single style and stigma. The ovary is superior; each cell 
has one axile placenta with numerous ovules, foliar in origin. The fruit 
“potato-apple” or “potato-ball” is a 2-celled, many-seeded berry, 
spherical or ovoid, and green or purplish in color. The seeds are small 
and kidney-shaped and are embedded in the green pulp of the fruit. 
The flowers are homogenous and are self-pollinated. They produce 
no nectar and are rarely visited by insects. In many varieties the 
flowers do not open at all, but soon wither and drop off. Most of the 
pollen is sterile. The potent grains differ from the sterile ones in being 
smaller and more regular in shape. 
ANATOMY 
It seems best, before beginning a discussion of ontogeny, to give in 
detail the anatomy of the partly mature plant, chiefly because it facili¬ 
tates the understanding of the early developmental history which at best 
is involved. 
THE STEM 
A cross section of a stem, at a stage when the leaves are nearly mature, 
shows (PI. 27, A) a circle of fibrovascular bundles, limited on the inside 
by a well-developed pith, on the outside by the endodermis and cortex. 
The pith is of uniform nature, but the cortex possesses near the periphery 
a layer of collenchyma of rather uniform width, as seen in Plate 29, A. 
Plate 29, D, illustrates the stem epidermis, which is one cell thick and 
separated from the collenchyma by a subepidermal layer also one cell 
thick. 
