402 MacDougal . — The Mechanism of Curvature. 
XXIII. Wortmann. — Zur Kenntniss der Reizbewegungen. Bot. Ztg. xlv, 
785,801,817,833. 1887. 
XXIV. Wortmann. — Einige weitere Versuche liber die Reizbewegungen 
vielzelliger Organe. Ber. d. deut. Bot. Ges., v, 459. 1887. 
XXV. Wortmann. — Zur Beurtheilung der Kriimmungserscheinungen der 
Pflanzen. Bot. Ztg., xlvi, 469, 485. 1888. 
XXVI. Wortmann. — Beitrag zur Physiol ogie des Wachsthums. Bot. Ztg., 
xlvii, 229, 245, 261, 277, 293. 1889. 
XXVII. Wortmann. — Ueber die Beziehungen der Reizbewegungen wach- 
sender Organe zu den normalen Wachsthumserscheinungen. Bot. 
Ztg., xlvii, 453, 468. 1889. 
EXPLANATION OF FIGURES IN PLATE XIX. 
Illustrating Prof. MacDougal ’s paper on the Mechanism of Tendrils. 
All the figures were made freehand from longitudinal sections of tendrils of 
Passijlora coerulea, and with the exception of Fig. 5, include the epidermis, 
collenchyma, and cortical parenchyma. 
Fig. I. Showing size, arrangement, and contour of cortical parenchyma-cells of 
concave side in free coils. Prepared from fresh material, x 350. 
Fig. II. Showing tissues of convex side in free coil. Prepared from fresh 
material. x 350. 
Fig. III. Tissues of concave side of active tendril before stimulation. Killed 
with acetic-alcohol and imbedded in paraffin. X550. 
Fig. IV. Showing tissue of convex side of active tendril before stimulation. 
Killed with acetic-alcohol, and imbedded in paraffin, x 350. 
Fig. V. Infolded end-walls of pith. Prepared from fresh material, x 300. 
Fig. VI. Showing contour of tissues of concave side after curvature. Killed in 
acetic- alcohol and imbedded in paraffin. x 350. 
Fig. VII. Tissues of convex side after curvature. Killed in acetic-alcohol and 
imbedded in paraffin. X350. 
