E. R. Saunders 169 



Discussion of the Significance of the Results. 



Apart from the addition to our knowledge of the factorial relations 

 involved which is gained from the observations here recorded, we are 

 able to look upon these results as marking a distinct advance in our 

 view, if not as to the nature of the factors themselves, certainly in 

 regard to the way in which we may suppose them to act. The question 

 whether it may become possible in the future to identify some material 

 component which we can point to as representing this or that factor 

 must be left to the chemist to determine. At the moment the most 

 promising line of investigation seems to me to call for the aid of the 

 physiologist, and until we have assistance in this field I doubt if in the 

 present case any further considerable progress can be made in the direc- 

 tion of distinguishing genetic behaviour from fluctuating variability 

 independent of factorial constitution. It may, however, serve to clear 

 the ground if we attempt to discover what inferences seem to be war- 

 ranted on this point from the facts already before us. 



In the first place whatever the factors already identified may stand 

 for in the Stock it is difficult to resist the conviction that they do not 

 produce their effects, solely by causing the production of some particular 

 substance which in their absence is not formed. Of particular interest 

 in this connection is a remarkable plant which appeared unexpectedly 

 in the course of the present work. The individual in question — the 

 only specimen obtained of its kind — was a beautiful example of a mosaic, 

 being in part fully hoary, in part glabrous. The seedling, an F^^ plant 

 from the mating RH^K x CRH, appeared to be a normal fully hoary 

 individual. Later however, after some 18 or 20 leaves had been formed, 

 two green lines indicating the absence of hairs were observed to extend 

 up the stem, and after widening and converging, finally to coalesce. 

 From this point onwards the mosaic character of the individual was 

 strikingly evident. Leaves arising from this smooth sector all showed 

 glabrous areas of larger or smaller size. In some one side of the midrib 

 would on both surfaces be hoary, the other glabrous. In others sharply 

 defined densely hoary grey patches would be scattered like islands over 

 the surface of the smooth green lamina, sometimes on one surface only, 

 sometimes on both, the areas being sometimes unrelated, sometimes 

 superposed (see PI. VIII, figs. 10 and 11). A noticeable feature of all 

 such mosaic leaves was the distortion or asymmetry of contour. Where 

 the midrib formed the demarcation line the one side would be well de- 

 veloped with the outline showing an even curved sweep, the other would 



