Apr., 1921] 
MCNAIR RHUS DIVERSILOBA 
191 
25. Schwalbe, C. On the active principle of Rhus diversiloba. Med. Rec. 63: 855. 1903. 
26. Schwalbe, K. Die giftigen Arten der Familie Rhus. Miinch. Med. Wochenschr. 49: 
1616. 1902. 
27. Strasburger, E., and others. A text book of botany. Eng. transl. by H. C. Porter. 
p. 122. London, 1898. 
28. Torrey, J., and Gray, A. A flora of North America i: 218. New York, 1838. 
29. Warren, L. E. Some observations on the pollen of poison sumach. Amer. Jour. 
Pharm. 85: 545-549- I9i3- 
EXPLANATION OF PLATES 
Plate III 
All figures have been reduced one half in reproduction and now show magnifications 
as follows: figure i, Xio; figure 2, Xio; figure 3, X23.3; figure 4, X470; figure 5, X91.65. 
Fig. I. Transverse section through the same stem as in figure 3. 
Fig. 2. Transverse section through a woody root. 
Fig. 3. Transverse section through a stem older than that of figure 5, showing annual 
rings with their varied formations of spring and fall growth. 
Fig. 4. Transverse section through mature leaf showing cystolith in palisade paren- 
chyma. 
Fig. 5. Transverse section through stem showing cork cambium; tracheal tube (T); 
pericycle with schlerenchyma cells or bast fibers and thin-walled pericycle parenchyma; 
phloem with resin duct {R); cambium (C); pith (P). 
Plate IV 
All figures have been reduced one half in reproduction and now show magnifications as 
follows: figure i, X23.3; figure 2, X23.3; figure 3, X470; figure 4, X23.3. 
Fig. I. Transverse section through a male flower near its base, showing 5 calyx leaves 
(C) with resin ducts (R), 5 petals (P) with resin ducts (R), 5 stamens (5), and the non- 
fertile ovule (0). 
Fig. 2. Transverse section through a female flower near its apex, showing 5 calyx 
leaves (C) with resin ducts (R), 5 petals (P) with resin ducts, 5 rudimentary anthers with 
neither pollen nor resin ducts, and the fertile ovule (O). 
Fig. 3. Transverse section through an unripe fruit near the seed, showing numerous 
crystals. Size of hexagonal crystal, 0.007 X 0.0025 mm. 
Fig. 4. Transverse section through an unripe fruit showing an abundance of resin 
ducts (RR). Diameter of largest resin duct, 0.0085 mm. 
