Jan. 13, 19 
Oe ? Dr. Shreve, 
I enclose mv Hat r ov .your 1939 collections and my carbon 
f which please return) of the Hat of Vhlte plants. This has been 
a very n’ce lot of plants to study and really I have gotten a It out of 
It, It Is great fun to work on the region. I have so many of 
the tyoes nd duplicates o' typos available that I really feel that 
I can clean up the taxonomy. I am certain that no other place could 
be half so good as the Cray Herbarium , as a place at Tfoich to write 
an account of the Chihuahuan Desert. I am more an more Impressed 
by the fact that the valleys in which Monclova and Saltillo are placed 
do not belong to our ares. The flora In thse places tee? Is that of 
Tfcievo Leon and Tamaulipss. Ill bet there are over 500 species known 
only in the valley near ?£. and S, and not known nor to he expected in 
our area , otherwise* ’?e should plan to draw our boundary from Cerneros 
Pass along the crest ' west ©c Daltlllo and al-nsr the hills we t of 
’'end ova . 9a ny o" the plants of the dry lower bahsdae about Saltillo 
we will find are included in our list since they are known from the 
hills about Cerneros and south of Parras, as well as in the range of 
hills west rsf the v lley. I am certain only of ^hls eastern limit 
for our region. The southern limit Is very Important for my work. 
Pl-ase do give me a boundary. H~w ab^ut arbitrarily deciding on 
the Tropic of Cancer. That would shut out much of the Valle Salado 
but it would save us deciding whet, he 1 ” or no the dry saline plains 
east o p SLP. should be Included. You have been down the whole 
length of our western limit. Cant you give me a boundary there ? 
You have not written me anything about the character of the desert In 
southern Durango. 
filth these lists finished, I must now write up the new soeclea. 
