164 ON BIASTREPSIS IN ITS RELATION TO CULTIVATION. 



to an unequal distribution of moisture in the soil, especially when 

 fresh farmyard manure is used. Then again, injury by birds or insects 

 gives rise to great differences among the seedlings. All these various 

 conditions have as their result that the young plants, after germi- 

 nation is over, soon show striking differences in development. Ac- 

 cording to the goodness or badness of the weather in the course of 

 the summer, these differences either become more marked or they 

 tend to disappear. And then, if the plants are crowded so as to 

 touch each other, the existing differences become accentuated, the 

 more vigorous developing rapidly at the expense of the weaker. 



Much more in the same strain might be added: but what has 

 been said suffices to prove that the individual differences between 

 plants growing on the same bed are mainly caused by the inequality 

 of the conditions under which they have been developed. If now 

 the most vigorous and best-developed individuals be selected as 

 seed-bearers, it is almost certain that they are those which have been 

 the most highly nourished throughout their lives. Selection in this 

 case means the selection of the best-nourished. 



It would appear to be quite permissible to extend this conclusion 

 to the case of biastrepsis. During the ripening of the seeds, during 

 their germination, and then during their subsequent development, 

 the individuals of the same sowing of the same seed are exposed to 

 very different conditions of life, although every effort may have 

 been made to secure uniformity in this respect. And it is these diffe- 

 rences of external conditions which determine which and how many 

 of the seedlings shall develop twisted stems, the seedlings belonging, 

 of course, to the proper hereditary breed. 



The plants with the most strikingly twisted stems which are 

 selected as the seed-bearers are thus generally those which have 

 been the most highly nourished. And as this mode of selection is 

 pursued in successive generations, so the best-nourished plants 

 have for many years had the bestnourished individuals as their 

 ancestors. Thus the influence of nutrition accumulates as the gene- 

 rations succeed each other. 



I may add that I have made similar observations in the case of 

 other plants and of other types of monstrosities. 



D. Summer-sowings. 



The sowings associated with the observations which have been 

 already given were made between the beginning of March and the 

 middle of May, and the particular time of the sowing was without 



