LAMARCKIANA SEMIGIGAS. 693 



bility of some degree of latent mutability existing in numerous other 

 cases, where plants have been considered until now as immutable. 



14-Chromosome offspring of Oenothera semigigas. 



These have ordinarily the type of Oe. Lamarckiana and should 

 be expected to come true to their type after self-fertilization. This 

 proved to be true in the cultures of the offspring of three such 

 plants and of two others, whose chromosomes had not been counted. 

 Each experiment embraced about 60 flowering individuals. Mutants 

 or aberrant types were not seen in the first-named three lines, but 

 included in the two others, 1 auricula and 1 cana in the first, and 2 

 lata, 3 albida, 2 scintillans and 2 cana in the second instance. Leaving 

 these aside, all of the 300 plants were uniform and pure Lamarckiana. 



Among the offspring of Oe. semigigas x tardescens I had noted 

 one plant which had the external marks of Oe. rubrinervis (de Vries 

 1924 b, p. 225). I sowed its seeds after fertilization and had in 1924 

 a progeny of 59 plants, 54 of which were like the parent and as 

 brittle as my race of that name, while five were mutants (2 oblonga 

 and 3 liquida). 



Conclusion. 



The offspring of Oe. semigigas, after fertilization with the pollen 

 of a velutina type, (biennis x Lamarckiana) velutina, tardescens or 

 blandina, shows the same hereditary constitution as the corres- 

 ponding older races. The dimorphic mutants split into Lamarckiana 

 and their own type (scintillans, cana, liquida, spathulata and pulla), 

 the sesquiplex forms give a uniform progeny besides about one- 

 half of empty seeds (oblonga, auricula, and the new form cana sesqui- 

 plex). Derivatives with 14 chromosomes also give a uniform off- 

 spring, with some mutants. Those with 16 or 17 chromosomes might 

 be expected to split into two or three forms each, but they repeat 

 their main type and give a second one only rarely and then mostly 

 in very small numbers of individuals. 



All in all, the mutants derived from Oe. Lamarckiana semigigas 

 are genetically constituted, as far as investigated, exactly like the 

 corresponding mutant races, directly sprung from the parent species. 

 Interchromosomal correlations have not been found between them. 



LITERATURE CITED. 

 Boedijn, K-, 1924. Die typische und herotypische Kernteilung der Oenotheren. 

 Zeitschr. f. Zellen u. Gewebelehre 1 : 265-277. 



