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University of California Publications in Agricultural Sciences [Vol. 2 



hybrids, but also of producing such hybrids artificially. From 

 the descriptions of the two families it is evident that they are 

 rather closely similar. Following is a table of comparison** of 

 the reproductive organs in Juglans and Quercus : 



Juglans 



Plants monoecius. 



Staminate flowers on lateral pen- 

 dulous catkins on last season's 

 wood; calyx irregularly 3 to 

 6-lobed; stamens numerous. 



Pistillate flotvers solitary or few in 

 a short terminal spike; calyx 

 4-lobed, adherent to the 1- 

 celled inferior ovary; styles 2. 



Fruit a 1-celled, incompletely par- 

 titioned nut, 1-seeded, the seed 

 so lobed as to fit the irregulari- 

 ties of the cavity, exterior of 

 nut covered with green and 

 fleshy or at length dry and 

 brown husk. 



Quercus 



Plants monoecius. 



Staminate flowers on pendulous (ex- 

 cept in one species) catkins 

 from buds of the previous sea- 

 son; calyx parted into several 

 lobes; stamens 4 to 12. 



Pistillate flower 1 in an involucre; 

 involucres 1 or 2 in the upper 

 axils of the season's shoot; 

 calyx adherent to the 3-celled, 

 6-ovuled ovary; ovary with 3 

 to 5 styles or stigmas. 



Fruit a 1-celled, 1-seeded nut, only 

 1 ovule maturing; seed with 

 thick, fleshy cotyledons; the 

 nut set in a scaly cup. 



From the above table it is evident that in gross structure 

 of flowers the two genera are closely similar. Of course, there 

 is always the possibility or likelihood that some feature in the 

 minute structure of the pistillate flowers or in the physiology of 

 fertilization may absolutely prevent hybridization between any 

 and all species of the two genera. The writer has not yet been 

 able to engage in the cytological study necessary to confirm or 

 deny this possibility. 



The first effort made was to search for chance natural hybrids 

 in the wild. In 1907 about four thousand nuts of Juglans cali- 

 fornica were gathered in Brea Cafion. They were taken from 

 trees standing close to coast live oaks. As they were planted late 

 in the spring they were slow in germinating and cutworms 

 destroyed many of them, but among two hundred that grew 

 during the summer of 1908, no aberrant forms appeared. No 

 further efforts in this direction were made, as the possibilities 

 of success were considered too remote to warrant the expense of 

 collecting and growing. 



6 Based on descriptions of the genera in Jepson 's The Silva of Cali- 

 fornia. 



