The following List of Grasses, accompanied by the very judicious and practical observations of the Corresponding Member of our Natural History Society, Mr. C. J. Croft, of the 1st Cavalry California Volunteers, was received by mail from Fort Goodwin, Arizona Territory, some little time since. From the same intelligent source, we have, from time to time, received many valuable specimens, preserved with uncommon care, and reaching us in a state quite unusual, even from localities far more favorably situated. We are very hopeful, we shall shortly be placed in possession of specimens of the seed of the _White Layia Mexicana_, for ornamental culture, as also of a species of native Potato, from the same indefatigable individual, who has also furnished us with a very interesting account of numerous species of the Cactus family, of that District. The Grasses of Arizona. BY C. J. CROFT, U. S. A. The grasses of this Territory, principally consist of four varieties: No. 1. (_Pleuraphis Jamesii_, Torr.,) is the lowland Grama which grows in great profusion along the valley of the Gila, and constitutes the principal feed for our animals, which do quite well upon it, moderately worked. No. 2. (_Aristida purpurea_, Nutt.) The highland Grama, growing upon the sand “mesas,” or highlands, seems to differ but little, if any, from that found in some portions of California. No. 3. (_Muhlenbergia pungeus_, Thurb.) Black Grama, or, “Grama China,” as vulgarly called by the natives, is the most valuable as feed; upon it animals will fatten. It grows on the highlands in sandy arid soil. I have never met any of this variety in the valley of the Colorado, and but very little in the territory of New Mexico. At this post we have had as many as 700 animals, and the scarcity of forage required us to herd our stock upon this grass during the winter. We were often obliged to make rapid and distant marches in pursuit of Indians, over a country almost impassable, yet our horses stood it well, fed only upon this grass. Our cavalry here had no grain during the entire winter. This Grama, like the other species, grows in bunches several feet apart, and the lower stalks are green during the winter season. No. 4. (_Sporobolus airoides_, Trin.) This grows in the valleys. A great portion of the Gila Valley is covered with it. Animals eat it readily when green; it is however a powerful diuretic. As a winter grass it is of no account. Besides these four enumerated grasses, the letter contained three others from the same locality: 1. _Panicum capillare_, L. 2. _Tricuspis pulchella_, Kunth.