_Castania sativa_, the commercial chestnut of Europe, in many varieties has long been cultivated in America and for nut production is without doubt the best of the well-known exotic species. It has no great timber value, however, and its disease-resistance, though higher than _C. Americana_, is scarcely great enough to warrant extended use as breeding material. The native chinquapin, _Castanea pumila_, in its bush and tree forms remains as the only promising chestnut not found in the Orient. While readily inoculated by artificial means, the chinquapins, especially varieties of the northern bush forms, quite often escape natural infection, doubtless because of their small size, smooth bark, and less liability to insect attacks. Chestnut breeding for nut improvement, chiefly by selection of native European and Japanese species, has been carried on in several diverse localities in the United States, with distinctly promising results but inter-pollinations have also been effected between most species and varieties, the outcome indicating that rapid improvement along the desired lines may be expected from crossing the really desirable types. In 1903 and succeeding years the writer made many careful pollinations of the native chestnut and the bush chinquapin with European and Japanese chestnuts in many varieties. Some hundreds of seedlings resulted, mostly showing a high level of promise as judged by their initial thrift and vigor of growth, but the appearance in 1907 of the Endothia disease among the plantings soon put an end to the work with the native and European chestnuts, as, with scarcely an exception, they quickly became infected. The crosses of chinquapin and Japan chestnut, however, showed considerable resistance as a whole, and a number of individuals have resisted infection until the present time, though constantly exposed to the disease, both at their locality of origin in New Jersey and since at Arlington farm, to which they were transferred in the second and third years of growth. Others have been attacked in greater or less degree, but show great powers of recuperation, sending up suckers that often fruit well by the third year. The resistant varieties show great promise as nut producers, coming into bearing when three or four years old from seed and producing abundant crops of handsome nuts, of excellent quality, four to six times as large and heavy as those borne by the chinquapin parent, ripening in early September before chestnuts of any kind have appeared in the market. These nuts have thicker shells than other chestnuts, are much less subject to attacks of the chestnut weevil and preserve their fresh and inviting appearance longer when gathered. The flavor varies somewhat according to the particular pollen parent of the different varieties, but is always agreeable in the fresh state when the nuts are properly cured. When boiled or roasted they are particularly sweet and pleasant to the taste.