CONTENTS. 



Page 



Introduction i 



Scope and purpose of the study l 



Pure species and hybrids examined 2 



Trichomes of Oenothera lamarckiana X Oenothera cruciata and of the parental 



lines 5 



Oenothera lamarckiana 6 



Oenothera cruciata 7 



Oenothera lamarckiana X Oenothera cruciata 9 



Comparison of trichomes of the Oenotheras 10 



Trichomes of Papaver hybrids and pure species 12 



Trichomes of the pure species 12 



Papaver somniferum X Papaver orientale 13 



Papaver somniferum X Papaver pilosiim 13 



Trichomes of Solanum villosum X Solanum guinense and of the pure species... 14 



Solanum villosum 14 



Solanum guinense 15 



Solanum villosum X Solanum guinense 15 



Pure species and hybrids of Juglans 17 



Leaves of the pure species 17 



Juglans californica 17 



Juglans nigra 17 



Juglans regia 18 



Trichomes of the pure species 18 



Juglans californica 19 



Juglans nigra 25 



Juglans regia 30 



Comparison of leaves and trichomes of Juglans, pure species 34 



Hybrids of Juglans 35 



Leaves of the hybrids 35 



Juglans californica X Juglans nigra 35 



Juglans californica X Juglans regia 35 



Trichomes of Juglans californica X Juglans nigra, first generation 37 



Trichomes of Juglans californica X Juglans regia, first generation 40 



Juglans hybrids, second generation 42 



Leaves of the hybrids 43 



Trichomes of the hybrids 44 



Measurements on the trichomes 52 



Juglans californica Y, Juglans nigra, second generation , 52 



Juglans californica X Juglans regia, second generation 55 



General comparison of trichomes in pure species and hybrids of Juglans 57 



Conclusions and results 61 



Summary 65 



in 



