70 HANS TEDIN 



flower colours in the field due to the great modifiability of the plants. 

 The wings of the light purple flowers change sometimes their colour 

 to nearly white with only a pale shade of light purple in the edges. 

 They get then easily confounded with the whites. The purple and 

 rose coloured flowers are modified in the same way. White (1. c.) says: 

 »Weather conditions, especially prolonged damp or rainy weather, 

 often wash out or suppress the development of the purple flower 

 colour, so that it resembles the pink, ana pinks are modified by the 

 same causes to white». I have never observed such a marked modifi- 

 cation of purple and rose, hpwever, nor have I any decided opinion 

 as to the cause. Last year, for instance, the first developed flowers 

 of 01001 (first part of July) were almost white, while the following 

 ones (latter part of July to late in the autumn) developed the hght 

 purple colour quite typically, although the weather was mostly cloudy 

 wäth hardly any sunshine and at times with heavy rains. When growing 

 oMer the purple and rose coloured flowers get at bluish tinge. They 

 are now easily confounded with the violet and light purple flowers. 

 Hence the marking of flower colour should always be done on flowers 

 just opened. 



* Very much damage and very great difficulties have been caused 

 by thrips, the small injurious insects belonging to Thysanoptera. Its 

 attacks on the buds often prevent them from opening. In this way 

 all the F, and F3 material in 1914, 1915, 1917 and 1918 was destroyed. 

 Some of the Fi and F2 families are lost or more or less damaged 

 every year, due to the attacks of these insects. No reliable figures 

 can be obtained from such material, and these families have to be 

 discarded. Nevertheless individuals from certain of these Fo progenies 

 have been selected and sown to F3 in some cases where the flower 

 colour could be determined with certainty. This explains, for instance, 

 the circumstance that the number of purples sown in 1912 (tab. 3 — 9) 

 exceeds the number of purples obtained in Fo in 1911 (tab. 1). 



The sowing was done by hand in four rows with 20 cm. between 

 the rows and 10 cm. between each grain in the row; twigs were used 

 as support. Although the plants stood so closely and were entwined 

 in each other the determining of the number of plants in the different 

 colour classes segregated could be done without greater difficulties, if 

 only two qualified persons were helping each other; for one person 

 it is hardly possible. 



The difficulties stated in the above make it evident, that it is 

 almost impossible to avoid errors in the marking. Besides the confu- 



