Physiological Studies in Plant Anatomy 267 
2. Wound cork formation, the scar left at leaf fall and natural 
cork formation all show the following causal sequence: first, the 
blocking of a parenchymatous surface, usually by a deposit of suberin 
or cutin formed in presence of air; secondly, the accumulation of sap 
at the parenchymatous surface thus blocked; and thirdly, the con¬ 
sequent development and activity of a phellogen amidst this 
parenchyma. 
3. The pericyclic origin of a periderm must be attributed to the 
presence of a functional endodermal barrier when the phellogen is 
formed. 
4. Special cases, such as the general absence of periderm forma¬ 
tion in the cortex of roots, in the axes of aquatic plants, and in 
leptosporangiate ferns, provide additional evidence for the correct¬ 
ness of the causal sequence stated above. 
5. In the case of cork formation in leaves experimental evidence 
is supplied to show that the meristem formation depends upon a sap 
pressure within the tissue. 
6. Further experimental evidence is also supplied, confirming 
previous statements to the effect that the preliminary suberisation 
depends primarily upon air. 
y. It is further shown that if the parenchymatous surfaces are 
artificially blocked by experimental methods, a subsequent sap 
pressure may produce meristematic activity as a result of which 
tissues like normal periderm may be formed, save that the walls are 
not suberised. 
REFERENCES 
(1) Appel, Otto. Zur Kenntnis des Wundverschlusses bei den Kartoffeln. 
Ber. dev deutsch. Bot. Ges. 24, pp. 118-122. 1906. 
(2) Bary, de. Comparative Anatomy of Phanerogams and Ferns. Oxford, 1884. 
(3) Basecke, Paul. Beitrage zur Kenntnis der physiologischen Scheiden 
der Achsen und Wedel der Filicinen. Bot. Zeitung, 86, p. 25. 1908. 
(4) Blackman, F. F., and Matthaei, Gabrielle L. C. On the reaction of 
Leaves to Traumatic Stimulation. Annals of Botany, 15, pp. 535- 
546. 1901. 
(5) Devaux, H. Recherches sur les Lenticelles. Ann. des Sci. Nat. vin fc 
Ser. 12, pp. 1-240. 1900. 
(6) Douliot, H. Recherches sur le Periderme. Ann. des Sci. Nat. vn e 
Ser. 10, pp. 325-395. 1889. 
(7) Haberlandt, G. Zur Physiologie der Zellteilung. I. Sitzungsher. der Konig. 
Preuss. A had. dev Wissensch. Berlin, pp. 318-345. 1913. 
(8) - Zur Physiologie der Zellteilung. II. Sitzungsher. der Konig. Preuss. 
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(9) —— Zur Physiologie der Zellteilung. III. Sitzungsher. d. K. Preuss. A had. 
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