OENOTHERA LAMARCKIANA MUT. VELUTINA. 175 



race of 0. rubrinervis and a specimen of the third generation of 

 0. bland ina. One part of the seeds was sown in 1914 and another 

 in 1915. In the first year I had 60 plants with 32 per cent blandina, 

 and cultivated 18 laeta and 7 blandina until the ripening of their 

 fruits. In the last named year I had 77 specimens, of which 61 per 

 cent were blandina and of which 5 laeta and 5 velutina were left to 

 flower. All in all, the cultures embraced 137 plants, with 45 per 

 cent blandina. The others were all subrobusta and not different 

 from the subrobusta cultures of those years resulting from other 

 crosses. 



0. blandina x 0. rubrinervis. — For this cross I used two speci- 

 mens of 0. blandina of the third generation in 1913, the one being 

 a pale green and the other a normal color. In 1914 each of the cul- 

 tures embraced 60 plants, of which 25 flowered. The percentages 

 for blandina were 48 for the green, but only 20 for the pale parent. 

 For this reason I repeated the latter culture in 1915 and obtained 

 from 70 plants 47 per cent blandina. The types of subrobusta and 

 velutina in these cultures were exactly the same as those from the 

 reciprocal cross. 



The percentages given are obviously of the same type as those 

 for the splitting into laeta and velutina and come as near to equality 

 for the two types as may be expected under ordinary conditions of 

 cultivation. I propose to grow the second generation next summer. 



The viability of the seeds of 0. Lamarckiana mut. velutina. — Besides 

 the external differences between our new mutant and the parent 

 species, there is another mark which lends a high interest to the 

 new form. This is found in the seeds. The seeds of 0. Lamarckiana 

 differ from those of almost all other species (with the exception of 

 0. suaveolens) in containing a large proportion of empty grains, 

 even under the most favorable conditions of life. More than one- 

 half of the seeds have no germ at all, although externally they are, 

 as a rule, not distinguished from the normal ones. Renner 1 ) has 

 studied the development of these empty seeds and found that their 

 germ is fecundated and undergoes one or two cell divisions,, but 

 then stops and dies off. He considers this phenomenon as a heredi- 

 tary character of the species. It runs parallel, in this respect, to the 

 rudimentary ovules described by Geerts, which are characteristic 

 of the whole group of the Oenotheras. Besides this type of empty 

 seeds a less or larger number usually occur which stop their develop- 



*) Renner, O., Befruchtung und Embryobildung bei Oenothera Lamarckiana. 

 Flora 7 : 115-150. 1914. 



