184 HANS RASMUSON 



under lip and whitish with onlj' small streaks of lilac on the upper 

 lip of the corolla. One of the plants (505 b), however, had a large 

 lilac spot on each of the two leaves of the upper lip. This one was 

 crossed with a plant with flowers of the normal type. This cross was 

 505 c X 505 b (hybridisation IV), the spotted pollen plant used being 

 the self green plant discussed in the hybridisation VI. All the Fi-plants 

 had a spot on each of the leaves of the upper lip, which, however, did 

 not reach the size of that in the pollen plant 505 b. Thus the presence 

 of the spot showed dominance, although perhaps not complete, to its 

 -Q5 J, 505 c absence. In F^, there was a distinct 



segregation. Two plants had flowers 

 without spot and the other four had 

 flowers with a spot. Of these four only 

 one, however, had a large spot, the other 

 three having a somewhat smaller. Per- 

 haps the first one was a homozygote and 



p^T 1 i^ f /- *• t • the other three heterozygotes. The num- 



rig. 1. Mowers of C. tinctoria. -^ ^ 



bers found agreed well with the theo- 

 retical values (1,5 : 1,5 : 3). Therefore a gene may be supposed which 

 when present produces a spot on each of the two leaves of the upper 

 lip of the corolla. When in homozygotic state the spot probably beco- 

 mes larger than when it is present in heterozygotic state. 



As the spotted plant 505 b was used in the hybridisation VI a 

 segregation w^ould be expected here as well. I have not investigated 

 the Fi-plants as to this character but in Fo plants with spots as well 

 as plants without spots were found. Only 5 plants were controlled 

 but of these 3 had spots, 2 were without them. One of them, VI — 5 

 — 1, with spots gave by self-pollination one plant with spots. Another 

 Fs-plant, VI — b — 5, w'ith a small spot gave a progeny consisting of one 

 plant without spots and others with a more or less large one. Alsa 

 here the results agree well with the theoretical expectations. 



SUMMARY. 



1. A white-flowered variety of CoUinsia bicolor was crossed with 

 the normal type, the flowers of which are lilac on the under lip and 

 whitish on the upper lip. The stem of the white-flowered variety was 



