402 BOTANICAL GAZETTE [November 



LITERATURE CITED 



1. Britton, N. L., North American trees. 1908. p. 31. 



2. BucKHOUT, W. H., Formation of annual rings of wood. Forest Quarterly 

 5:259. 1907. 



3. BiJSGEN, M., Bau und Leben unserer Waldbaume. 1897. p. 62. 



4. Coulter, J. M., and Chamberlain, C. J., Seed plants. 1901. 



5. GoFF, E. S., The resumption of root growth in spring. Wis. Sta. Rept. 

 1898:220-228. j^g. (5. 1898. 



6. Hartig, R., Das Holz der deutschen Nadelwaldbaume. 1885. p. 35. 



7. : , Anatomie und Physiologie der Pflanzen. 1891. p. 262. 



8. Hartig, T., Bot. Zeit. 18:829. 1858. 



9. Hastings, G. T., When increase in thickness begins in trees. Science, N.S. 

 12:585. 1900. 



10. Mer, E., Sur les causes de variation de la densite des bois. Bull. Soc. 

 Bot. France 39:95. 1892. 



11. Penhallow, D. p., Anatomy of the North American Coniferales with 

 certain exotic species from Japan and Australia. Amer. Nat. 38: 243. 1904. 



12. Reuss, H., Beitr. zur Wachstumsthatigkeit des Baumes nach praktischen 

 Beobachtungsdaten des laufenden Starkenzuwachsganges an der Sommer- 

 rinde. Forstlich. Zeitschr. 2:145. 1893. 



13. Strasburger, E., Die Angiospermen und die Gymnospermen. 1879. 



14. WiELER, A., Uber die Periodizitat im Dickenwachstum des Holzkorpers 

 der Baume. Bot. Zeit. 56:262. 1898. 



EXPLANATION OF PLATES XXIV AND XXV 



Fig. I. — Cutting taken from apical shoot of tree III April 15, 1910; 

 cambium in the resting condition; X50. 



Fig. 2. — Same, but cutting taken about i m. from the apex; cambium in 

 the resting condition; X 50. 



Fig. 3. — Same, but cutting taken about 2 m. from the apex; growth in 

 evidence to the extent of one or two partly formed tracheids; X50. 



Fig. 4. — Cutting taken from apical shoot of tree III May 4, 1910; growth 

 just beginning at A; compare with fig. i; Xso. 



Fig. s.^Same, but cutting taken 1 m. from the apex; growth slightly 

 more advanced; compare with fig. 2; X50. 



Fig. 6. — Same, but cutting taken from the apex; growth in evidence to 

 the amount of 3 or 4 tracheids; compare with fig. 3; Xso. 



Fig. 7. — Cutting taken from tree III April 15, 1910, about 3 m. from the 

 apex; growth in evidence to the extent of one or two partly formed tracheids; 

 Xso. 



Fig. 8. — Same, but cutting taken about 4 m. from the apex; growth in 

 evidence to about the same extent as in fig. 7 ; X 50. 



