24 STUDY OF NUTS - MICROSCOPIC IDENTIFICATION. 



many improved varieties in recent years, as a result of which much 

 interest has been aroused in pecan culture, especially in the eastern 

 Gulf and South Atlantic States. 



As a native of the forest the pecan does not cover as large an area 

 as do many other species of forest trees. It is common in the bottom 

 lands adjacent to the Mississippi and its tributaries from Davenport,, 

 Iowa, and Terre Haute, Ind., on the north over a rather broad area, 

 extending southwestward to the lower Rio Grande. 1 



It has been introduced to a very large extent into the States of 

 Georgia, Florida. Alabama, the Carolinas, and to some extent in 

 lower Virginia. Interest in pecan growing in the northern States 

 is just now being aroused by the origin of several choice varieties in 

 southern Indiana, northern Kentucky, and lower Virginia, which 

 give considerable promise to the pecan future in sections of similar 

 climatic, soil, and moisture conditions. 



Pecans of the named varieties are as yet marketed in their natural 

 condition, without stain or polish. A large portion of the native 

 nuts are dipped in a reddish-colored dyeing solution, dried, and 

 polished, after which they are placed upon the market. Nut-crack- 

 ing establishments are located in the pecan sections and principal dis- 

 tributing points of the northern States, the product of which, graded 

 as whole or broken half kernels, is sold in the markets of the country 

 at large. 



Lazenby 2 reports 38 to 49 per cent of kernels, according to the 

 size of the nuts. It is the opinion of the writer, however, that the 

 proportion of kernels is dependent more upon the thickness of the 

 shells, which is an individual or varietal characteristic, than upon 

 the size of the nuts. Four commercial samples examined gave 40^ 

 40.2, 40.4, and 42.8 per cent of kernels. These samples represented 

 nuts of different sizes, from small to large, in the order reported, but 

 each contained both thick and thin shelled nuts, thus bringing the 

 result somewhere near the average for the species. In the named 

 varieties the proportion of kernel depends upon the variety and 

 usually runs from 45 to 55 per cent, but occasionally reaches 62 or 

 63 per cent of the nut. 



Histology. The epidermal cells of the integument average about 

 75 y, in length and are usually from one-fourth to one-half as broad> 

 much less commonly isodiametric (fig. 8, A) ; cells 120 [ji or more in 

 length are sometimes found. The walls are thin and appear to be 

 slightly beaded. On account of the thickness of the outer layer of 

 spermoderm it appears from the surface much like a mass of paren- 

 chyma. Stomata are fairly common. They are very nearly circular 



Pecan and its Culture, U. S. Dept. Agr., Bureau of Plant Industry Bui. 251. 

 2 Proc. Soc. Prom. Agr. Sci., 1903, p. 101. 



