ARNOLD ARBORETUM, HARWARD UNIVERSITY,Jamaica plain, Mass, December 27, 1898.My dear Muir:Your letter which I got two or three days ago sounded a little sad I think. I am not surprised, however, that a man who would rush through Texas, New Mexico and Arizona without stopping even for a day to look at some of the most interesting trees in the world should be a little dejected. It is pretty evident that you cannot be trusted to travel alone and that in future I shall have to be your constant companion.I pass my time now thinking about [illegible] and hear of or see a new species nearly every day. It looks like a hopeless or at least an endless job; but what perhaps is more difficult is to get the flowers of that Birch-tree which grows at the h...