494 Dale . — Origin , Develop ment , and Morphological 
common to the stem and petiole, as far as this is possible 
on account of the difficulties which occur owing to torsion. 
Hence the sections are chiefly longitudinal. It will be con- 
venient to trace the growth of the tubers by describing these 
sections from the apex of the stem downwards. 
A median longitudinal section through the apex of a shoot, 
shows at each node a young leaf arching over the buds in its 
axil. Most of these buds, which generally number as many 
as six or • eight, are the young spikes of flowers. At the 
young nodes the buds are undifferentiated and placed on a 
more or less conical mass of tissue in the leaf-axil. 
Four or five nodes from the apex the differentiation of the 
buds has proceeded so rapidly that the two or three nearest 
to the stem have attained to the condition of elongated 
peduncles bearing lateral flower-buds. The youngest buds, 
nearest to the subtending leaf, are still rudimentary. The 
peduncles are arranged in pairs in the leaf-axils, the older 
anterior and the younger posterior. The youngest buds, 
posterior to the peduncles, are solitary. At this stage there 
is no trace of a tuber in the leaf-axil. 
Somewhat lower down the stem the first beginning of the 
tuber is seen as a slight swelling below the youngest bud 
(PJ. XXVI, Fig. i). 
Sections through a node in which the young tuber is visible 
to the naked eye show that it is at this stage already dis- 
tinctly separated from the surrounding tissues. Between the 
youngest of the peduncles and the tuber, in the series of 
sections examined, there was a single median vegetative bud, 
much less developed than those which form the peduncles. 
The tuber itself had two rudimentary buds lying in the 
median plane, one near the point of attachment of the tuber 
and the other more remote, and posterior. These buds caused 
angular projections on the tuber. The tissue lying a little 
below the cortex, between the buds, and especially between 
the posterior bud and the attachment of the tuber, was meri- 
stematic, and the most rapidly growing part of the structure. 
In a young stem in another plant, grown under peculiar 
