146 
AMERICAN JOURNAL OF BOTANY 
[Vol. 8 
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DESCRIPTION OF PLATE II 
The material selected for the sections was fixed in a chrom-acetic fixative (i percent 
by weight chromic acid in water, 0.5 percent glacial acetic acid by weight). Suitable 
pieces were then hardened by placing in alcohol of different concentrations in series of 
6 percent, 12 percent, 25 percent, 50 percent, and 75 percent, then in xylol and paraffine 
and finally in paraffine. Sections were then cut on the microtome in series, fastened to 
clean slides with egg albumen, stained with safranin and Delafield's haemotoxylin, and 
finally washed in absolute alcohol, in xylol, and mounted in balsam. By this treatment 
lignified and suberized walls were stained red and cellulose walls violet. 
The photomicrographs were made with an electric arc as the source of light. The 
amount of magnification was calculated by the aid of a ruled slide on the microscope stage 
and of a rule on the ground glass focusing screen, using the same lenses as were used in the 
exposure. The photomicrographs have been reduced 2% times. 
A. Transverse section through a lateral leaf rib, showing a resin duct. The resin duct 
is 0.0053 mm. in diameter. The shortest distance to the bast ring which surrounds the 
resin duct is 0.0056 mm. X 168.4. 
B. Young shoots showing simultaneous expansion of leaves and flower panicles (reduced 
one fifth). 
C. Transverse section through a woody root. X 7.5. 
D. Transverse section through a staminate flower near the apex showing five calyx 
leaves with resin ducts, five petals with resin ducts, five anthers showing absence of resin 
ducts and presence of pollen, and the non-fertile ovule. X 40.9. 
E. Transverse section through a green stem, showing epidermis with its trichomes, 
collenchyma, cortical parenchyma, pericycle with sclerenchyma cells or bast fibers, and 
thin-walled pericycle parenchyma. X 40.9. 
F. Leaf epidermis with attached club-shaped trichomes. (Size of trichomes 0.071 X 
0.0027 mm.) X 353-7- 
G. Transverse sections of petiole. The largest resin duct has a diameter of o.oi mm.; 
the smallest is 0.0044 rn^n- i^i diameter. The largest pith cells are larger than the smallest 
resin ducts. It is 0.02 mm. from the corner of the petiole section to the bast ring which 
surrounds the nearest resin duct. X 33-8. 
