KNOWLEDGE OF THE MUTATING OENOTHERAS. 33 



merely a dwarf or miniature gigas of the broad-leaved type. Different dwarf rosettes 

 show much variability in leaf-shape, the dwarf character being the only thing they 

 have in common. Schouten states that his plants of 0. gigas nanella showed the same 

 pathological conditions as his O. nanella^ but I have found no indication of it in my 

 cultures. It is evident that the dwarf character is directly due to an inherited germinal 



change in both cases. 



The percentage of dwarfs in my cultures of O. gigas was large. Out of 339 plants, 

 one lot contained 4'28 per cent., another lot 8*76 per cent., while a third lot of only 



■ 



fifteen plants contained 10"9 per cent. Schouten's (1908) cultures of 0. gigas yielded 

 in 1906 2'01 per cent. 0. gigas tianella^ or 24 plants in 1196 ; and in 1907, among 

 about 1000 gigas plants, which were chiefly the offspring of selected individuals of the 

 previous year, appeared a total of 1*87 per cent, dwarfs, one culture yielding as high as 

 14' 81 per cent. The meaning of this behaviour is not yet clear. 



All individuals of the O. gigas of DeYries's cultures are descended from one indi- 

 vidual mutant. Nilsson (1909) reports obtaining another O. gigas mutant in a culture 

 of 30 0. Lamarchiana which were the offspring of one individual *. In the following 

 year this 0. gigas individual yielded 8 plants, all having the characters of O. gigas. 



In 1909 I obtained from the Botanical Garden at Palermo, Italy, a packet of seeds 

 under the name Oenothera cognata. A portion of these seeds were sown in 1911, and 

 yielded 56 rosettes. The young plants apparently belonged to a new and unknown race. 

 Their leaves bad very long petioles, and the blades were ovate with broad tips, gradually 

 tapering to the petiole. Some of these leaves are shown in PI. 3. fig. 40. They 

 resemble type (1) in the younger rosettes of 0. LamarcUana or 0. laevifolia as already 

 described. As previously stated, I have never observed this type of leaf in cultures of 

 DeVries's gigas. As the rosettes of O. cognata develop, however, there is a sudden 

 transition to the 0. gigas type of leaf, and the mature rosettes — after more of the second 

 type have been produced and those of the first type have died away— are absolutely 

 indistinguishable from 0. gigas. PL 3. fig. 40 represents the transition stage, when 

 both types of leaf are present. These plants were all biennials, and hence produced no 

 seeds, but a fresh sowing has yielded a few plants, from which the characters will be 

 more fully determined. The number of the chromosomes has not yet been examined f. 



The mature rosettes of this culture exhibited the same variations as my cultures 

 of O. gigas, though the extremes of variation were not observed. Three dwarf rosettes, 

 corresponding to O. gigas nanella, also occurred. 



Enquiry at the Botanical Garden at Palermo elicited the information that the race 

 had been derived in cultivation, apparently being descended from a single individual 

 mutant. They have since lost the strain. It is evident, then, that this was an inde- 

 pendent mutation, and it remains to be seen whether the race differs constantly from 

 O. gigas in its earlier ontogenetic stages, for the mature rosettes are identical with that 

 form. Prom this and other data, some of which will be referred to in this paper, it is 



See also Nilsaon (1912) for further data, 

 t The chromosome number for typical plants has since heen found to be 28. 



SECOND SERIES. — BOTANY, VOL. VIII. 



V 



