BULLETIN 231] WALNUT CULTURE IN CALIFORNIA. 165 



of these California nigra trees there are always some typical of the 

 species, and some years a great many. Moreover, the progeny of certain 

 trees are almost all straight nigra and the proportion of such normal 

 seedlings is in inverse ratio to the opportunities for crossing with other 

 walnut species. 



Juglans nigra was planted quite commonly with eastern nuts in Cali- 

 fornia in the very earliest years of the American occupation. Thus 

 there are many large trees of the species now growing in the State. 

 The trees are in almost every instance closely associated with specimens 

 of both California species and also more or less with the English walnut. 

 Many nuts from these original trees have been planted, and again those 

 from the next generation, down to three or four or perhaps more gener- 

 ations. The result has been that about the older towns in the central 

 and northern part of the State, trees may be found which present every 

 degree of gradation between nigra and the California species and also 

 many trees which have only slight resemblance to either, but might 

 easily be classed as entirely new species if their origin was not known. 

 It is hardly worth while to describe the individual trees of this sort, 

 so numerous are they in the State. In some cases it is difficult or impos- 

 sible to distinguish between hybrids and true nigra, as the nuts and 

 foliage are very similar. Most of them, however, can be pretty certainly 

 picked out on account of their unusual vigor of growth, the fact that 

 they come out earlier and hold their foliage later than true nigra, 

 a different aspect of the tree and foliage which cannot be definitely 

 described, and the fact that the nuts are somewhat smoother and vary 

 in other ways from those of true nigra, although various trees of the 

 latter species have nuts of very different form and size. 



The Royal hybrid is very different from the Paradox in regard to 

 productiveness, being in almost every instance very precocious and an 

 unusually heavy bearer of nuts. The most productive nut trees which 

 we have ever seen are some of these Royal hybrid walnuts. In favor- 

 able seasons the ground beneath them will be covered several deep with 

 nuts, while there are still so many on the tree that it is difficult to see 

 where there could have been room for those which are upon the ground. 



The cross between nigra and the northern California species is com- 

 monly illustrated in all the towns above mentioned. The Burbank Royal 

 is an unusually fine tree, being of tall, erect growth, with a clean, uni- 

 form trunk, and of exceptionally vigorous and rapid development. It 

 is a heavy bearer of very large nuts of a type more closely resembling 

 those of nigra than those of the California species. The 'nuts, in fact, 

 would pass for a fine large type of nigra, but are smoother than those of 

 the usual type. They are deeply and much grooved, but not ridged to 

 any extent. 



