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ü 



were sown in October, under uniform conditions, in the experimental 

 part of the Botanical Garden, approximately equal numbers of 

 each. Many of the fruits did not germinate, and some of the young 

 plants that came up, died in the course of the first year. In the 

 Spring of 1917, there were 174 living and their leaftimes were recorded 

 in that way, that the plants were observed on the 19th, 24th, 

 27th, and 31st of May. Each time, it was recorded for the des- 

 cendants of each mother plant, how many were: 1) fully in leaf, 

 2) half out of the bud, 3) not out of the bud ; — that is to say, that 

 the leaves had not begun to unfold. The results are given in Tables 

 1, 2, 3, and 4, which correspond to the 19th, 24th, 27th, and 31st 

 May respectively. The first column gives the numbers of the young 

 trees: columns a, b, and c, give respectively the wholly open, half 

 open, and not open cases. To facilitate the comparison, the numbers 

 are given as per cents. 



The Tables show a striking correspondence between the 

 mother and descendants with regard to leaftime. That 

 parallelism shows that leaftime, that is, early or late leaftime, in 

 the cases in question, is genotypically determined. That 

 external conditions can influence the leaftime needs no demon- 

 stration. The woods are green at different times in different years. 

 That is also seen in these experiments, in that even the earliest trees 

 here, are, absolutely seen, late, on account of the fact that it is 

 young trees we have to deal with, growing in the cold and heavy 

 soil which is offered by the experimental part of the Botanical 

 Garden. 



Even if the pollination of the mother plants had been controlled, 

 it would, since it takes so long before the beech flowers, be a dif- 

 ficult, or rather, a slow process, to attempt by the analysis of the 

 descendants to determine the nature of the genotypic factors 

 controlling early or late leaftime. 



Let us meanwhile assume that the genotypic basis of, for in- 

 stance, "very early leaftime", is a single factor, and either dominant 

 or recessive. Of the four theoretically possible cases to follow, 

 two are excluded by the results of the experiments. The mother 

 plant 880, that has very early leaftime, can not be heterozygous 

 with regard to the leaftime factor if the factor be regarded as 

 recessive : and it can not be homozygous if early leaftime be regarded 

 as dominant, for, in that case, all the descendants must have shown 

 very early leaftime, which was not the case. The two other possibili- 

 ties are both to be considered, and it is to be remembered that the 

 tree may or may not be self-pollinated. And given that, it is prob- 



