Variability as a Nutritional Phciionicnon. 519 



we can easily observe that in the Um1)clH ferae tlie num- 

 ber of umbels is small in proportion as the twif,^ bearing 

 them is weak. 



> With regard to Papavcr somnifernm polyccphaliim 

 we saw in the first part that it was not possible to separate 

 selection from nutrition. I mean, if we choose our seed- 

 parent, paying attention to the greater or less beautiful 

 development of the circlet of secondary fruits, we in- 

 evitably chose either the strongest or the weakest ]jlants. 

 There seems therefore no escape from the conclusion tbat 

 the variability of this circlet is simply a plienomenon of 

 nutrition and that selection in one direction merely 

 chooses the most highly nourished individuals ; and in the 

 other, the most poorly nourished. 



In an investigation of this kind one must take into 

 account the susceptible period. One organ will pass 

 through this period earlier; another later, as I have 

 pointed out in the case of the poppy referred to. The 

 same is true of oats and wheat in relation to the amount 

 of water in the soil. In the first vegetation-period this 

 condition influences the number of internodes in the 

 haulm as well as in the panicles, or ears. At the time 

 of shooting, the amount of water in the ground afifects 

 the length of the internodes, and the size of the parts of 

 the inflorescence (the foundations of which have already 

 been laid down by this time) as well as the greater or 

 less fertility of the ears. Much water at the time of 

 shooting increases the amount of straw as well as the 

 yield in grain. ^ 



Jahrb. f. w. Bot., Bd. 30, 1897, p. 453 and W. Haacke. Ilnhciikcluui:s- 

 mechanische Untersuchungcn, Biol. Cenlralbl., 1900. 



^VoN Seelhorst, Journal fiir Landwirthschaft, Bd. 4S. p. 163: 

 Reference in Botan. Ccntralbl, 1900, No. 41, Bd. 84, p. 54. 



