WALNUT. 17 



one or two cell layers. The stomata are subtended by rather small 

 respiratory cavities. The inner periderm layer is 20 pi or more thick 

 and consists of compressed cells forming a parenchyma tissue which 

 lacks distinctive character and in some places contains large vascular 

 bundles. 



The endosperm comprises a rather thin layer, 16 to 40 pi thick, 

 closely joined to the kernel. It usually consists of a single cell layer, 

 which at intervals becomes thickened to two or three layers. The 

 cells are usually much elongated. The epidermis of the cotyledons 

 consists of cells smaller than those of the endosperm. In surface 

 view they are angular and vary considerably in form, while the walls 

 are thin and slightly beaded. This layer lies close to the parenchyma 

 cells Ovf the cotyledon, averaging about 50 to 60 (x in diameter. These 

 cells are sometimes arranged in lines perpendicular to the surface of 

 the kernel or of the convolutions in the interior of the cotyledon. 

 The surface of these convolutions is covered with an epidermal layer 

 similar to that of the exterior of the cotyledon, and the narrow in- 

 closed space sometimes contains a layer of hyaline matter probably 

 derived from the endosperm. In addition to oil, the embryo con- 

 tains aleurone grains which are seldom more than 10 pi in diameter. 

 Their structure is not characteristic. 



BUTTERNUT OR WHITE WALNUT. 

 (Juglans cinerea L. ) 



The butternut is a well-known native tree producing elongated 

 pointed nuts having a thick shell and a very rough surface, to which 

 the outer tissues of the pericarp cling tenaciously. The oily kernels 

 are of high quality, but the nuts of most trees are of little commercial 

 importance on account of the thick shell. It is not improbable, how- 

 ever, that the present search by nut growers for individual trees bear- 

 ing nuts of thin shell and of high quality, from which to propagate, 

 w r ill result in the development of valuable varieties and an increased 

 production of this nut- According to Lazenby x butternuts contain 21 

 per cent of kernels, while Woods and Merrill found only 13.6 per 

 cent. 2 The latter is probably abnormally low, as the writer obtained 

 22.1 per cent. 



Histology. The outer cells of the seed coat are considerably more 

 angular in appearance than those of the Persian walnut, and also, 

 as a rule, decidedly larger (fig. 3, A). While their average diameter 

 is about 50 pi, cells 100 pi in length are occasionally seen. Stomata 

 are quite numerous and measure 40 to 60 pi in length and TO to 80 \L 



1 Composition and Waste of Fruits and Nuts, Proc. Soc. Prom. Agr. Sci. 1903, p. 101. 



2 Nuts as Food, Maine Agr. Exper. Sta. Bui. 54, p. 81. 



55137 Bull. 16012 3 



