50 
The Relations of Pinus edulis and P. monophylla-—/'///^/^ mono- 
phylla, Torr. and Frem., was described in Fremont's " Report of the 
Exploring Expedition to the Rocky Mountains in the Year 1842, 
and to Oregon and Northern California in 1843 and 4," Washington,- 
1845, House Doc. No. i66, p. 319. PL 4, The specimens upon which 
the description was based were obtained from '' Northern California, 
longitude 111° to 120°"; mostly from an area now included in the 
State of Nevada. Among the specimens brought in by Fremont were 
some in which the leaves were both single and double, but the double 
leaves were rare exceptions to the general rule. 
In the years 1857, 8 and 9, and later, I passed in many direc- 
tions through most of the country occupied by Pinus edulis and 
the so-called P. monophylla, in the northern states of Mexico, 
Arizona, New Mexico, Colorado, Utah and Nevada, and I found the 
facts in regard to the relations of these two forms to be essentially 
these : 
■ The chosen habitat and home of Pinus edulis is the belt or area of 
dry country lying between the saline and treeless portion of the 
** Great Basin" in Nevada and Utah and the higher and better 
watered mountain ranges which border or divide the desert areas. 
In Southern Utah, between the summits of the Wasatch and the 
Western sage plains in Western New Mexico and Eastern Arizona, as 
well as some portions of Northern Mexico, the nut-pine attains the 
largest size and stands thickest on the ground. Here it ranges from 
20 to 50 feet in height, has a trunk sometimes two feet in diameter 
and is universally two-leaved. In Nevada and Western Utah the 
trees are smaller in size, more scattered, and usually have but a single 
cylindrical leaf. Where the areas of these two varieties meet it is 
very common to find trees in which the foliage is about equally 
divided between the single and double forms. Hence it would seem 
that the single-leaved variety is a somewhat dwarfed and depauperate 
form, the eifect of aridity of climate; and the single solid leaf is 
apparently an exhibition of the tendency so conspicuous among 
desert. plants to reduce the ratio of surface to mass in the leaves, or 
the parts of the plant which perform the functions of leaves. In 
Cactus, Ildocantha^^ Canotia, Ephedra, etc., vi^e see the extreme form 
of this self-protective modification, no leaves but an epidermis w^hich 
does what little there is for leaves to do, and in Cactus, Holocantha, 
etc., a formidable array of spines to protect this from possible injury. 
Dr. Torrey, to whom more than twenty years ago I showed my speci- 
mens of Pinus monophylla and P. edulis, agreed with me in consider- 
ing them only varieties of one species. Mr. Thomas Meehan, in his 
interesting note lately published on this subject * considers the two 
forms as of common origin, but as constituting distinct species, 
seems to me, however, they are typical varieties of common origm 
and shading into each other, and of unusual interest, since their rela- 
tionship can be easily traced, and, if I am right, the causes which have 
produced the differences are easilv comprehensible. 
J. S. Newberry. 
It 
*Proc. Phila. Acad. Nat. Sciences, I884, p. 295, and this journaL 
