SUMMARY. 65 



SUMMARY. 



(1) The trichomes of the following- hybrids, and of the pure parental 

 species, were passed under observation: Juglans calif ornica X Juglans 

 nigra, F l and F 2 ; Juglans calif ornica X Juglans regia, F t and F 2 ; Oenothera 

 lamarckiana X Oenothera cruciata, F 2 and F 3 ; Papaver somniferu m X Papaver 

 orientate, F,; Palaver somnifertim X Papaver pi lo sum, Fjj Solatium villosumY. 

 Solatium guinense, F t , F 2 , and later generations . 



(2) The Oenothera hybrid inherits characters from both pure parents, 

 but does not revert to either line. 



Three types of trichomes, all of which are unicellular, are found in both 

 parents and in the hybrid Oenothera. Those of lamarckiana are larger than 

 those of cruciata, while the corresponding trichomes are, in the hybrid, of 

 an intermediate size. Both in the hybrid and in the pure parental lines 

 the trichomes which occur on or in the close vicinity of the veins of the 

 leaf are larger than those between the veins of the same leaf. 



The distribution of the trichomes is unlike in the two pure lines and in 

 the hybrid. In lamarckiana both types of glandular trichomes are found 

 on stem, leaf, and capsule; in cruciata the pear-shaped trichome occurs on 

 the same regions, but the club-shaped trichome is found on the capsule 

 only. In the hybrid the club-shaped trichome only occurs on the capsule, 

 in this particular exhibiting- a cruciata character, but no other type of tri- 

 chome is found on the capsule in which the hybrid is different from either 

 pure parental line. The peculiar quality of distribution is held to indicate 

 the independence of each type of trichome as a character. 



(3) Two strains of Papaver hybrids were examined, both of which were 

 sterile, so that the first-generation plants only were available. 



Only one type of trichome is found in Papaver, both in the hybrids and 

 pure species, which has, in the hybrids, an intermediate structural character. 



(4) In the Solanum hybrid and pure species 2 types of trichomes are 

 found, but of these one type only is common to both parental lines and 

 the hybrid. The second type occurring in the hybrid is inherited from 

 the guinense line. 



Although as reg-ards the trichomal character the Solanum hybrid has 

 unilateral inheritance, in another regard it possesses a new characteristic, 

 the flavor of the fruit, which, in all the material examined, was seen to be 

 a constant character. 



(5) In Juglans, pure species, 4 types of trichomes, 3 of which are mul- 

 ticellular and glandular and 1 unicellular and lifeless, are found in each 

 species. Nigra and nigra derivatives have, in addition, a form peculiar to 

 themselves. Each form of trichome has a manner of development to which 

 it adheres with great constancy. Numerous measurements show that the 



