ENGELMANN REVISION OF THE GENUS PINUS, ETC. ibl 



■cult, therefore, to properly circumscribe the species ; for the present I feel 

 obliged to unite with it even P. Hartivegii and a number of others already 

 included by Parlatore. Only a closer study on the Mexican mountains will 

 decide whether or not several well characterized species may be hidden 

 among them. All those that I could examine have numerous and strong 

 bundles of strengthening cells under the epidermis and also near the ves- 

 sels, but none around the ducts. 



19. P. Torreyana, Parry, has the same structure of the leaves. The 

 name was published in the Botany of the Mexican Boundary, 1859, ^""^ i® 

 therefore older than P lopJioserma, Lindl. of i860. 



20. P. Arizonica, Engelm. in Bot. Wheeler, p. 260, has also this struc- 

 ture and is thus distinguished from /'./owiferosa, besides being five-leaved. 



21. P. Engelma7ini, Carnere, Conif. p. 356; P. macrophylla, Engelm. 

 in Wisliz. Mem. p. 103, note 25, is a tree onlj^ known from Wislizenus' 

 single specimen gathered in 1846 on the mountains of Cosiquiriachi, west 

 of Chihuahua, where it is said to be abundant. The name was changed by 

 Carriere because it clashed with Lindley's prior one; this, however, is 

 considered by Parlatore to be a form of Mo7itezu7nce, but which I have not 

 been able to examine. Our plant differs from this species by having its very 

 stout leaves in threes and fours and very rarely in fives, in the strongly 

 developed strengthening cells under the epidermis and also around the 

 ducts, and in the form of the cone. Parlatore does not mention it. 



22. P. ponderosa, Douglas, a variable and wide-spread species of West- 

 -ern North America, several forms of which have been described as distinct. 

 The only one which may perhaps claim specific recognition is our var. 

 Jeffreyi [P. Jefreyi, Murr.), characterized by its darker more finely cleft 

 tai-k, glaucous branchlets, paler foliage, and much larger cones, with rather 

 slender sharp recurved prickles and larger seeds; but it seems that inter- 

 mediate forms unite it with the typical one. Another form which deserves 

 notice is var. scopulortim, of the Rocky Mountains, with shorter and often 

 Ijinate leaves and smaller cones (see Engelm. in Fl. Calif. 2, p. 125). 



23. P. Canarietisis, Ch. Smith, is perhaps more nearly related to P. 

 Laricio than to fotiderosa. The articulation of the 4 involucral bracts is 

 a curious feature which it has in common with our P. t-esinosa (see p. 168). 



24. P. ChiJiuahiiana, Engelm.. first described from the mountains of 

 Chihuahua, but now repeatedly found in Arizona, is well distinguished 

 from all its relatives by its deciduous sheaths. 



25. P. Laricio, Poir. Strengthening cells around ducts and in bundles 

 all around leaf; the typical form has slender leaves and is tender in culti- 

 vation. Var. Monspeliensis or Pyretiaica (not to be confounded with No. 

 .15, as the author of that species himself and many later botanists have 

 done) has slender leaves with scarcely any strengthening cells around the 

 leaf, and is more hardy than the species. Var. Aastriaca or nigra is per- 

 fectly "hardy; it has the stoutest leaves of all the forms, with abundant 

 strengthening cells. A specimen in Herb. Kew, Birmah, Griflith 4993, 

 may belong here, thus extending the range of the species far into Asia. 



