Mutations in Other Families. 



291 



lata and very often, especially if the seeds are not sown 

 too thick, of O. nanella. 0. albida can also be recognized 

 very early. 0. oblong a and O. rubrinervis often cannot 

 be identified until much later : and 0. scintillans later 

 still. In fact it was quite an exception when I recognized 

 one of the last named in the pans at all with sufficient 

 certainty : when they were being transplanted they were, 

 commonly, simply taken for weak plants. 



Fig. 51. A mutation in a seed-pan. The plant in the middle is 

 an O. lata mutant. Tlie whole culture arose from a cross be- 

 tween O. Lamarckiana and O uaneUa. to which two types all 

 the rest of the plants in this figure belong. 



The superficial area of soil contained in these pans 

 is 25 X 25 centimeters. From % to % cubic centimeters 

 of seed is sown in them. Under these conditions the 

 plants have ample room when they are young. But if 

 they grow to an age at which the mutants amongst them 

 are recognizable they become much too thick for it to be 



