372 Cooke and Schively on Observations on the 
transferred to the hard bast. It is this great development of 
bast fibres that gives the stem its stiff inelastic nature. It 
probably was in order to form an external protection to the 
enlarged phloem region, that such a great development of 
hard bast occurred. The whole bundle arrangement is evi- 
dently intended to allow the free passage of sap out into 
the stem at all places through its course, and to insure the 
abundant and widespread storage of food all along the stem. 
Tue TuBER. 
Sections made through a large mature tuber present an 
extremely irregular and complicated aspect. Very striking 
is the great development through the parenchyma of thick- 
ened cells identical with the “hard bast” of the aerial stem 
bundles. These cells evidently are not a part of the true 
bundle system, and must originate in periblem rather than 
in plerome tissue. The bundles show a most confused 
and irregular arrangement, running in all directions and 
planes apparently. The phloem of a bundle is greatly in ex- 
cess of the xylem, and shows a tendency to spread out and 
lie in separate patches, while the xylem of each bundle seems 
always concentrated in a single area. Many of the bundles 
show an internal duplication with reversed order, phloem, 
xylem, xylem, phloem, succeeding each other from without 
inwards. In such a case, an area of thickened yellow 
stained cells often intervenes between the two xylem areas, 
and the whole may have resulted from fusion of two bun- 
dles. An internal phloem is almost always present, often 
in excess of the outer phloem mass. 
A wide ring of the thickened, so-called “hard bast” cells 
lies below the narrow cortex, being quite regularly inter- 
rupted by thin-walled parenchyma cells passing in toward 
*These rhizome sections were double-stained with Kleinenberg’s 
hematoxylin and Bismarck brown, the thickening then taking on a 
yellow or brown stain. 
