54 PREFATORY. 



We have been enabled to present in this Second Part, plates of some ten kinds of Oak 

 never before figured : namely, Q. Palmert, turbinella^ tomentella^ Macdonaldi and its variety 

 elegantula, Q. Fendleri^ Jacobin Gilbertiy venusiula, and the polycarpa form, or rather state 

 of Q. dtimosa. The other three here taken up anew, Q. undulata^ Gambelit, and Garryana., 

 although figured in earlier works, were in need of more thorough elucidation. From this 

 list of names it will be seen that these later thirteen plates should surpass, in point of 

 scientific value, the twenty-four earlier issued. 



It is a matter of some regret that, of several of the forms to be illustrated we had no 

 acorns. The time of year at which our journeyings had to be made was unfavorable to 

 the collecting of these. They are not well formed, as a rule, before September or October ; 

 and we were obliged to pass from the fields where oaks chiefly abound, before the end of 

 July. But in general the characteristics of the oak-species reside more in the outlines, 

 texture and duration of foliage, in the bark and wood, and in the bearing and aspect 

 of the tree as a whole, than in acorns. There are many instances in which closely related, 

 yet quite distinct species, have acorns nearly or precisely alike. Hence these, although 

 always to be desired, are not always indispensable to the satisfactory limitation and sure 

 identification of species. 



We should have liked well to have been able to produce plates of Q. Emory i of 

 Arizona, and of the rare Q. Sadleriana of the Siskiyou Mountains in southern Oregon. 

 But neither the necessary materials of these, nor of Dr. Kellogg's <2, vacciniifolia were 

 available. 



In the new elaboration of those shrubs of the Rocky Mountains previously re- 

 ferred to Q. undulata^ we have received most efficient help from Dr. N. L. Britton of 

 Columbia College, New York, who has in charge the Torrey Herbarium wherein are 

 preserved the types collected so long ago by Dr. James and Mr. Fendler. To enable us 

 to determine the geographical limits of Q. Garryana and Q. Jacobi, Mr. John Macoun, 

 Botanist to the Canadian Geological Survey has given us the privilege of inspecting the 

 bundle of specimens accumulated by the Survey ; and Mr. Charles V. Piper of Seattle, 

 Washington has favored us with all that he has collected in his region. To these 

 gentlemen we would here offer our grateful acknowledgments. Like services rendered 

 by friends nearer home will find record elsewhere in the work. 



EDWARD L. GREENE. 



University of California, 

 May 14th, 1890. 



