11(5 Phifsiologlcal Pn-detcDnination 



Harris (3u & 3i) in a very elaborate statistical investigation has 

 experimented in the opposite direction by submitting a race of beans 

 {Phaseolus vulgaris) to recurrent starvation conditions for three genera- 

 tions in order to determine whether any accumulated effect was trans- 

 mitted through the seed when the race was finally returned to normal 

 conditions. His "starvation" conditions were obtained by growing the 

 plants in fields in which the soil barely sustained the given species. 



He arrived at the conclusion that statistical constants showed an 

 unmistakable, though slight, influence resulting from the treatment of 

 the ancestors upon the race when returned to normal conditions. He 

 records this influence as mainly shown by a decrease in the number of 

 pods per plant and in the number of ovules per pod, but by no modifica- 

 tion in average seed-weight. The direct effect of the environment was 

 of the same nature, but far more pronounced. 



Gain (23) discussing the results of Raulin (60) concludes that a change 

 in the chemical nature of the soil is favourable. Plants grown in different 

 soils from generation to generation produce a larger average weight 

 of seed than plants grown from generation to generation in the same 

 kind of soil^. 



The results obtained by Raulin appear to be in contradiction to those 

 of most other workers and to general experience with regard to cereals. 

 Thus according to Hicks and Dabney(4i), although a marked difference 

 in crop is frequently noted when seed is transferred to a different type 

 of soil, from that in which it was grown, this difference is often in the 

 negative direction. They state that {I.e. p. 308) "Experiments in 

 growing oats have shown that certain varieties raised on a light soil 

 were the most productive if sown on a similar soil, while the same 

 varieties of seed, if grown on heavy soil, showed a preference for heavy 

 soil." 



With regard to the grasses, according to Tracy's (i.e.) experience, 

 the character of the soil exercises little influence upon the character of 

 the seed; climatic conditions acting upon the parent plant, however, 

 have a marked effect upon the "potentiality" of the seed produced. 



'■ "II y a un maximum et un minimum d'influcncc corrcspondant a unc ccrtainc 

 succession des divers sols (humus, sable, argile, calcaire). 



Les maxima repondent, pour Ic Blc, aux changements suivants: graiues cultivees dans 

 I'humus, doivent vcnir de Targile; celles destinces au sable doivent venir dii calcaire; 

 celles pour argile, du sable; celles pour calcaire, du sable. 



Les minima repondent aux changements: graines cultiv6es dans I'liumus, venant du 

 calcaire ou do I'liumus; en sable, venant de I'humus on du sable; en argile, venant do 

 Ihumus ou do I'argile; en calcaire, venant du calcaire on dc rhumus." 



