354 Origin of Each Species Considered Separately. 



many thousands of plants can be accommodated on a few 

 square meters of ground up till the time when the mu- 

 tants have to be planted out. 



But if the characters do not develop whilst the plant 

 is young, it is a very different matter indeed. In this 

 case 40 to 50 is the maximum number of plants that 

 can flower on a square meter, and that is a high estimate. 



When this is the case the plants must be cultivated 

 on an enormously extensive scale before we can enter- 

 tain the smallest hope of seeing mutations. We become 

 dependent to a large extent on chance as in the case of 

 the first appearance of O. gig as. 



It is obviously for reasons of this kind that practically 

 all my mutations are recognizable as seedlings, whilst 

 the two new species which are found at Hilversum are 

 indistinguishable in their young stages from young 0. 

 Lamarckiana. 



Oenothera leptocarpa is the only exception to this 

 rule, at least it is the only one among those which have 

 arisen from the pure stock of O. Lamarckiana. Amongst 

 the crops raised from crossed seeds there were occa- 

 sional instances ; but it is often difficult in these cases to 

 distinguish mutations from the ordinary products of 

 crossing. 



0. leptocarpa cannot, even in pure cultures, be dis- 

 tinguished from O. Lamarckiana either as a seedling or 

 as a rosette or even at the period when it is first devel- 

 oping its stem. I have once or twice transplanted sup- 

 posed mutations as young plants and found them to be 

 O. leptocarpa. But as a rule I have not recognized them 

 until just before they flowered. 



For these reasons little can be said with certainty 

 about the frequency with which this form appears. The 



