52 VARIATION. 



viduals of the clone. The final height to which a four or five 

 year old tree grows is obviously the result of so many develop- 

 mental factors, influencing the relative strength of terminal 

 and lateral buds, influencing the time at which growth starts, 

 the length and number of internodes, that it would not be sur- 

 prising if this character, the absolute height of the topmost 

 point, were influenced for a great part by external circumstan- 

 ces. But the fact is, that in a row of 3 7 oung Taxus trees, or Ap- 

 ples, or Thuyas, which constitute one clone, the tips of all the 

 trees are almost exactly at the same level. The trees of one 

 clone are so much alike, that if they are not mutilated or mark- 

 ed in any way, it is next to impossible to find again an individ- 

 ual tree at the second inspection of a row. 



Now we believed at first, that this absence of variation in 

 clones was apparent, and greatly flattered by the fact that 

 these clones were all commercial-named sorts, which had been 

 selected because of one or more marked characteristics, so that 

 the contrast between the clones threw into relief the similarity 

 between the members of each clone. 



Therefore it was important to find instances where a great 

 many colones can be compared, each out out of one individual, 

 without any selection on external characters. It is the practice 

 of the most progressive firms that produce sugar-beet seed to 

 multiply their seed-bearing beets asexually. The firm of Kiihn 

 & Co in Naarden, Holland, do this consistently. Every selected 

 root is sprouted in a green-house, and ten rooted sprouts are 

 separately potted up, and later planted out in a row. In the 

 fields of this firm, every summer we can compare hundreds of 

 different clones, all grown with the same care in the same field. 

 The first thing which strikes us if we inspect such a field, is the 

 remarkable similarity between the ten members of each clone. 

 And on closer inspection we see, that even characteristics 

 which in an ordinary culture would assuredly have been looked 

 upon as the consequence of accidents, prove to be due to the 

 genotype of the plant, as all the ten individuals of the clone 

 present them. If one plant has a slightly wilted appear- 



