230 R. J. STEINHOFF 



Sargent, C. S. 1897. Silva of North America. Vol. XI. Coniferae (Pinus). 



Houghton Mifflin Co., Boston and New York. 163 p. 

 Shaw, G. R. 1909. The pines of Mexico. Arnold Arboretum Pub. 1. 29 p. 

 Streets, R. J. 1962. Exotic forest trees in the British Commonwealth. 



Clarendeon Press, Oxford. 765 p. 

 Wellner, C. A. 1962. Silvics of western white pine. U.S. Dep. Agr. , 



Forest Service.. Ini.ermountain Forest £ Range Exp. Sta. Misc. Publ. 



26. 24 p. 

 Wright, J. W. 1958. Characteristics and identification of the soft pines 



cultivated in the Philadelphia area. Morris Arboretum Bull. 9: 19-30; 



45-47. 

 Wright, J. W. 1959. Species hybridization in the white pines. Forest 



Sci. 3: 210-222. 



FLOOR DISCUSSION 



Discussion given here covers the previous paper by Dr. Kriebel. 

 Moderator Bingham withheld discussion on the Kriebel paper so the two 

 closely related papers could be considered at one time. 



BINGHAM: The floor is open for discussion on the North and Central 

 American white pines. 



STEINHOFK As a result of confusion over the taxonomic status of 

 variety chiapensis of Pinus strobus , or Pinus chiapensis , Dr. Kriebel and 

 I neglected to mention this variety or species in our oral presentation. 

 However, it is covered by Dr. Kriebel in his formal paper. It is of rather 

 limited distribution in Mexico, primarily restricted to tropical rain- 

 forest conditions. I doubt that it would be useful to very many other 

 people around the world who are working with white pines. On good sites 

 it does attain considerable size. I have seen trees 2-1/2 to 3 feet in 

 diameter, over 100 feet tall, but I don't know too much about its growth 

 requirements . 



DUFFIELD: Dr. Steinhoff, in a conversation this morning you mentioned 

 a newly-discovered and newly-described pine from Mexico. Taxonomically it 

 sounded as if it might belong in white pine Subsection Balfourianae . Will 

 you comment? 



STEINHOFF: At the outset I should caution that the proposed new 

 Mexican pine species {Pinus rzedowskii) is only now being published by 

 Xavier Madrigal and Miguel Caballero of the Section of Botany and Ecology, 

 Department of Silviculture, of the Mexican National Institute for 

 Forestry Research and of the Department of Statistics, National Forest 

 Inventory, respectively, Mexico D.F. These authors very kindly loaned 

 me a copy of their unpublished manuscript, complete with illustrative 

 photographs, and I hesitate to preempt their rights by discussing it. 

 However, because the presumably new species has great interest to persons 

 at this session of the Advanced Study Institute who should be alerted to 

 watch for publication, I'll presume to discuss it here. To answer 

 Dr. Duffield's question, P. rzedowskii is both similar and dissimilar to 

 the Subsection Balfouvianae pines. Perhaps the most interesting point 

 is its similarity to Section Parrya pines, especially to Subsections 

 Cembroides and Balfouvianae thereunder. Subsection Balfouvianae pines 

 {P. balfouriana and P. aristata) , Subsection Cembroides pines (pinyon 

 pines) of Section Parry a, as well as the new species, are all set apart 



I 



