500 Mr Compton, On Right- and Left- Handedness in Barley. 



The discrepancy between the two generations is only such as 

 would be removed by a turn-over of fifteen lefts to rights, 

 assuming the 1909 ratio to be absolutely accurate. 



In this connection it should be remarked that stability of 

 population with regard to certain characters occurs, in the 

 absence of selection, as a result of the Mendelian inheritance of 

 those characters *. Hence the occurrence of a stable ratio in this 

 case is not in itself incompatible with the inheritance of the 

 characters concerned in a Mendelian fashion : though of course it 

 does not necessarily tend towards such a view, other alternatives 

 being possible. 



II. The ratios for whole populations having been obtained, 

 the question arises as to the ratios given by individual spikes of 

 fruit on germination. In order to determine this a number of 

 ears of " Plumage Corn " barley were laid whole on wet blotting- 

 paper, and on germination the seedlings of each spike were counted 

 for rights and lefts among the first leaves. Each seedling was 

 classified according to : 



(i) The twist of the last foliage leaf below the spike, 

 whether right or left. 



(ii) The row of seeds in the ear from which the seedling 

 arose, whether odd or even. 



The percentages of left-handed seedlings for each individual 

 spike, in which a reasonable number of seeds (more than ten) ger- 

 minated, were calculated ; and curves were drawn expressing the 

 relation of these percentages to the frequency of each percentage. 

 The curves were obtained by plotting, at intervals corresponding 

 to every 5°/^, the number of percentages included in a range of 

 5% on either side. Thus the number plotted for 60°/^ is that of 

 the percentages between 55 7o ^^^ ^^ L' ^^^ number plotted at 

 65 7o is that of the percentages between 60% and 70°/^ : and so 

 on. The curve for spikes above l.h. last leaves is drawn as a 

 continuous line (the lower in the diagram) ; that for those above 

 R.H. last leaves as a dotted line : there were 86 spikes of each 

 class. The taller continuous curve is given by all the 172 spikes 

 taken together. 



The curves for the spikes above l.h. and R.H. last leaves 

 respectively differ somewhat in shape. The former is steeper and 

 narrower, and indicates less range of variability than the latter. 

 The curve for R.H. top leaves shows two slight maxima, with a 

 minimum where the other curve reaches its maximum. It would 

 be unwise to lay stress on these differences, however, as they are 

 not very pronounced. The total curve is of a form very usual 

 in studies of variability. It is practically symmetrical about its 



* Hardy, Science, N.S., xxviii. 1908, p. 49. 



