ENGELMANN — PINUS ARISTATA, ETC. 209 



In Colorado it is a fine tree, with tapering trunk and oval 

 outline, branching almost from the base, lower branches hori- 

 zontal, upper ones ascending; wood white, hard, annual rings 

 from \ to \ line, on an average i line wide ; trees become in 

 250-300 years about 1 foot thick. Leaves crowded towards 

 the end of the very flexible branches, persistent 5 or 6 years, 

 usually H-2^, very rarely 1 or 3 inches long; sheaths similar 

 to those of P. Strobus or P. Cembra, 8 1. long, deciduous. 

 Male amenta 4-5 1. long, forming a thick spike 10-12 1. long, 

 cones subcylindric, tapering to the end, 4-5 inches long, 2 

 inches in the largest diameter, on short peduncles; scales 

 12-14 1. long, 10-121. wide, squarrose; lowest sterile ones re- 

 curved ; fertile ones with deep impressions for the reception 

 of the seeds both on the upper, inner side and on the back, 

 the latter cavities partly formed by the large (4-6 1. long) 

 ligneous or rather corky bract. Seeds 4-5, rarely 6 1. long, 

 irregularly ovate or obovate; wing minute, not deciduous nor 

 adhering to the scale, as in P. Cembra, P. eclidis, etc., but 

 reduced to a persistent keel on the upper end and outer edo-e 

 of the seed ; embryo with 8 or rarely 9 cotyledons. 



Pinus albicaulis; P. cembroides, Newberry, Pac. P.P. 

 Pp. 6, Pot., p. 44, c. /c, 7W7i Zi/cc, an alpine species from 

 the Cascade Mountains, in Oregon, may be a western form of 

 this species, though I am inclined to consider it as different, 

 and intermediate between P. flexilis and P. Ce7nbra, distin- 

 guished by the pubescent branchlets, few scattered teeth on 

 the edges of the leaves, and especially by the short oval cones 

 with thick squarrose scales pointed with a knob. The name 

 is suggested by the color of the bark of the tree, which is 

 "as white as milk." 



While studying the Coniferaa of the Rocky Mountains, I 

 was led to investigate the characters of the different types 

 which LinnaBiis had comprised in his genus Pinus. '1 he 

 great master himself had at one time thought proper to di- 

 vide that rather incongruous mass, considering Abies as 

 distinct from Pinus, reuniting them, however, afterwards. 

 Since then many botanists have investigated this interesting 

 subject, and while some of the highest standing — I mention 

 only the names of Endlicher and Hooker — have adhered to 

 the Linnaaan circumscription of the genus, others of no less 

 authority have thought it more natural to recognize the dis- 

 tinctions already made by popular language, and some of 

 them adopted by the older botanists. The first who more 

 thoroughly examined the question was Link, who (Linnsea 



Tsuga, considering all these as subdivisions of the genus 

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