Oenothera Lata. 415 



ing to 0.01% or less, or mounting to 2% or more. Ex- 

 ternal conditions therefore probably affect the propor- 

 tion in which O. lata arises from O. Lainarckiana. What 

 these conditions are is a subject for future enquiry. 

 Perhaps they exert their influence only during the ripen- 

 ing of the seed or during germination (See p. 263) but 

 probably they come into play at or before fertilization. 

 In order to give some idea of the range of variations 

 of these ''mutation coefficients" I give a list containing 

 the figures which have already been given (§§ 2-7) to- 

 gether with some new observations. 



INDIVIDUALS OF OENOTHERA LATA WHICH HAVE ARISEN 



BY MUTATION. 



I. FROM O.LAMARCKIANA. 



LAMARCKIANA FROM: DATE TOTAL 



SEEDLINGS 

 O. LATA % LATA 



Main line of descent, p. 224 1888-1890 25,000 8 0.03 



" " '• " 1895 14,000 73 0.5 



" " " " 1896 8,000 142 1.8 



" " " " 1897-1899 3,500 6 0.2 



Lateral branch, p. 262 1895 10,000 168 1.7 



An annual culture 1897 4,132 11 0.3 



A biennial culture 1897 164 8 5.0 



II. FROM CROSSES. 



O.Lam.x0.7ia7iella 1897-1899 8,283 22 0.3 



O.Lam.xO.gigas 1899 100 2 2.0 



O. Lam. y^O. biennis 1900 80 1 1.0 



6>.Z,aw. (from crosses; p. 300) 1896 4,600 7 0.2 



III. FROM OTHER FAMILIES. 



O.Lam.irom O.laevifolia 1889 400 3 0.8 



O.laevifolia 1894 1,500 2 0.1 



O.rubrifiervis 1894 96 2 2.0 



O.scintillans 1896-1899 7,872 38 0.5 



If we examine these figures closely we make rather 

 an interesting discovery. A high figure (5%) is only 



