154 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION. 



ville, Winters, Chico, and almost all the other towns of this portion of 

 the State, the northern California black walnut and the eastern black, 

 Juglans nigra, have been very commonly planted during the last sixty 

 years. The original specimens of nigra came from nuts brought from 

 the East and Middle West, and such trees are typical in every way of 

 their species. Among the younger trees, however, of later generations 

 which grew from nuts obtained from these eastern and California trees 

 growing more or less near together, numerous hybrids may be found, and 

 indeed after two or three generations in California it is almost impossible 

 to find a true type of Juglans nigra. 



Another very common cross is that between various species of black 

 walnut and the English walnut, which cross with great frequency in 

 California wherever the species grow at all close together. These two 

 crosses, that of California black on eastern black and California black on 

 English, received considerable prominence several years ago through the 

 introduction by Luther Burbank of trees of these two types, to which he 

 gave the names respectively of Royal and Paradox. These names, in the 

 absence of any others, have been quite generally taken up in California 

 to designate trees resulting from crosses of this sort, so that now by the 

 name Paradox is generally understood any hybrid tree resulting from a 

 cross between English and black walnuts, while Royal means popularly 

 any hybrid resulting from a cross between two different species of black 

 walnut. Trees of both of these crosses, and all sorts of mixtures and 

 degrees between four or five different species of Juglans, are not uncom- 

 mon in the State, and the particular strains introduced by Mr. Burbank 

 are sim'ply two very good examples of hybrids which have likewise 

 originated spontaneously in various parts of the State. 



That these trees are true hybrids and not simply variations due to 

 environment or other factors is evidenced in many ways, as may be seen 

 in the following discussion. 



PARADOX HYBRIDS. 



If the nuts from a black walnut tree of any species which stands near 

 an English walnut tree or grove be planted, the resulting seedlings are 

 apt to show a varying percentage of individuals of decidedly different 

 appearance from those of the black walnut. This difference consists in 

 a more or less marked resemblance to English walnut seedlings, the 

 trees having bark and leaves much resembling those of the English wal- 

 nut, and, in general, a very similar aspect to the latter species. In their 

 first year these seedlings may or may not differ decidedly in rate of 

 growth from the straight black walnut seedlings, but after the first year 

 in almost every case they show a more rapid development and within the 

 first four or five years they assume a size and rapidity of growth several 



