36 



HEREDITY AS ILLUSTRATED BY TRICHOMES. 



diameter. Like the other walnut hybrid (the Royal) this is a rapid grower; 

 the wood is fine-grained, and the annual rings are relatively wide. The 

 Paradox, unlike the Royal, however, bears little fruit. 



The leaves of the first generation are extremely variable in number of 

 leaflets, in size, and in many other particulars. Leaves with 3, 4, 5, 6, and 

 7 pairs of leaflets were selected for photographing (plate 7). 



The number of pairs of leaflets are said by Mr. Burbank to reach as 

 great a number as 19, though I did not see leaves with so great a number. 

 Measurements on the extreme variation of the leaves were not made, but 

 observation would indicate that the range may easily exceed 500 per cent. 



The leaflets vary in outline from ovate to broadly ovate. The apices 

 are acuminate or abrupt; sometimes they taper much as in the pure species 

 Juglans calif ornica. The bases are abrupt or even cordate; none are broadly 

 cuneate, as in pure species referred to. The leaf -margins are remotely 

 serrate. In all specimens examined the veins of the dorsal surface are 

 prominent. The leaf-surfaces are usually smooth, although they may also 

 be roughened. Thus each leaflet shows characters of both pure lines. 

 Whether a similar condition will be seen to obtain in the later generations 

 can not at present be stated. 



The great tendency of the leaves of the Paradox hybrid to vary has been 

 remarked by Mr. Burbank, who tells me that in company of two eminent 

 scientists he selected 400 leaves or leaflets easily recognizable as different 

 from one another. 



Table 14. — Leaves of Juglans californica X Juglans nigra, F^, compared with 

 those of the pure species. 



Table 15. — Leaves of Juglans californica X Juglans regia,Fi, compared with 

 those of the pure species. 



