34 



Latent and Sciin-Latoif Characters. 



Selection and nutrition have as usual a great effect 

 on half races. I shall not deal exhaustively with thjs 

 point until the end of this part, but will give here a brief 

 discussion of the general principles underlying it in order 

 to prepare a proper understanding of the question. 



Our discussion of the phenomena of fluctuating vari- 

 ability in the third part of the first volume led us to the 

 conclusion that selection and nutrition usually operate 

 in the same manner on the individual characters of plants. 



5 6 7 8 9 10 II 12 13 14 



Fig. 2. Influence of selection and nutrition on the half 

 race Raiinncnlus bulbosiis scmiplcnns. A, Half Curve 

 after several years of culture. B, Curve of the I2 best 

 individuals ( i. e., those richest in petals). C, Curve of 

 the best plant.^ 



Positive selection and plenty of food enhance the devel- 

 opment of a character, whilst selection in a minus direc- 

 tion or defective nutriment operate in the opposite direc- 

 tion. 



Polycephaly in Paparcr soinnifcrum behaves in this 

 way,^ and, as we shall see later on, all the other anomalies 

 which have been tested do so, as well. Half curves can 

 thereby be transformed into unilateral ones (Fig. 2), either 



^Ber. d. d. hot. Ges., Vol. XII, 1894, Plate X, Fig. 4. 

 ''Vol. I, Part I, pp. 135-143. 



