Nov., 1921] ENSIGN — ^ VEIN-ISLETS AS AN AGE DETERMINANT 
441 
2. No correlation was evident between the age of the following plants 
as indicated by their trunk diameters and the vein-islet area of their leaves: 
Fagus caroliniana Fernald and Rehder; Castanea dentata Borkh.; Berberis 
vulgaris L.; B. Thunbergii DC, and Vitis viilpina L; 
BIBLIOGRAPHY 
1. Benedict, H. M. Senile changes in leaves of Vitis vulpina L. and certain other plants. 
New York Agr. Exp. Sta. (Cornell) Memoir 7: 281-370. 1915. 
2. Child, C. M. The process of reproduction in organisms. Biol. Bull. 23: 1-39. 1912. 
Senescence and rejuvenescence, pp. 481. Chicago, 191 5. 
3. Conklin, E. G. Cell size and nuclear size. Jour. Exp. Zool. 12: 1-98. 1912. 
The size of organisms and their constituent parts in relation to longevity, senescence 
and rejuvenescence. Pop. Sci. Mo. 83: 178-198. 1913. 
4. Ensign, M. R. Venation and senescence of polyembryonic Citrus plants. Amer. Jour. 
Bot. 6: 311-329. 1919. 
5. Hertwig, R. Ueber Korrelation von Zell- und Kerngrosse und ihre Bedeutung fiir die 
geschlechtliche Differenzirung und die Teilung der Zelle. Biol. Centralb. 23: 194- 
223. 1903. 
6. Jennings, H. S. Age, death and conjugation in the light of the work on lower organisms. 
Pop. Sci. Mo. 80: 563-577. 1912. 
Effect of conjugation in Paramecium. Jour. Exp. Zool. 14: 279-391. 1913. 
7. Minot, C. S. The problem of age, growth and death, pp. 280. New York, 1908. 
8. Schuster, W. Die Blattaderung des Dicotylenblattes und ihre Abhangigkeit von 
ausseren Einflussen. Ber. Deutsch. Bot. Ges. 26: 194-237. 1908. 
EXPLANATION OF PLATE XXIII 
All figures are drawings made from the projection of the cleared and stained leaves. 
X 38. 
Fig. I. Venation of a leaf from 6-year-old barberry {Berberis vulgaris). 
Fig. 2. Venation of a leaf from i-year-old barberry {Berberis vulgaris). 
Fig. 3. Venation of a mature leaf from undetermined species of Vitis. 
Fig. 4. Venation of grape leaf {Vitis vulpina) having a trunk diameter of 1.3 cm. 
and showing 6 annual rings. 
Fig. 5, Venation of a leaf from chestnut {Castanea dentata) having a trunk diameter 
of 38 cm. 
Fig. 6. Venation of a leaf of grape {Vitis vulpina) having a trunk diameter of 10 cm. 
and showing 25 annual rings. 
Fig. 7. Venation of a leaf from grape {Vitis vulpina) having a trunk diameter of 0.8 
cm. and showing 5 annual rings. 
Fig. 8. Venation of a leaf from grape {Vitis vulpina) having a trunk diameter of 
5.2 cm. and showing 17 annual rings. 
Fig. 9. Venation of a leaf from grape {Vitis vulpina) having a trunk diameter of 
6.4 cm. and showing 18 annual rings. 
Fig. 10. Venation of a leaf from chestnut {Castanea dentata) having a trunk diameter 
of 3.7 cm. 
