582 IOWA ACADEMY OF SCIENCE 



For assistance and advice in the above work acknowledgment 

 is respectfully made to Dr. L. H. Pammel and Dr. J. N. Martin. 

 For specimens used the writer is indebted to Dr. C. S. Sargent, 

 Doctor Setchel, Mr. 0. W. Newman, Dr. T. C. Fry, Prof. H. M. 

 Hall, Mr. II. D. Petheram and Mr. E. Peck Greene. 



LITERATURE CITED. 



Sargent, Charles Sprague, Manual of the Trees of North Ameri- 

 ca, pp. 35-101. 



i'ngdmann, George, A Synopsis of the American Firs. Trans. 

 Acad. Sci., St. Louis, III, pp. 593-602. 



Bertrand, C. E., Anatomie des Gnetacee's et des Conifers. Ann. 

 Sci. Nat. Bot., 20, 1874, pp. 5-153. 



McNdb, W. It., Remarks on the Structure of Leaves of Certain 

 Conifers : Proc. Irish Acad., II, 1875, 209-213. 



Sharp, Seymour S., Notes on the Determination of Rocky Mt. 

 Conifers: Torreya, 15, No. 1, 1915. 



Coulter, J. M., and Bose, J. N., Synopsis of American Pines, 

 based on leaf anatomy: Bot. Gaz., Vol. II, 1886, 256-262 

 and 302-309. 



Botanical Laboratory, 

 Iowa State College. 



