[Vol. 2 



270 ANNALS OF THE MISSOURI BOTANICAL GARDEN 



treated at various stages of development now await germina- 

 tion and test. 



The differences between the two surviving derivatives of 

 Scrophularia described in this paper may well be due to such 

 differential action. It is to be seen that if egg or sperm were 

 affected singly the resultant seed into which these elements 

 might enter would be hybrid. Even if both were acted upon, 

 it is by no means to be taken for granted that the effects in 

 the two would be equivalent. The F2 of rufida was identical 

 in the cultures described, while the F2 of albida presented 

 some modifications, the status of which is not yet established, 

 as both were open pollinated in the Fi. Very little informa- 

 tion as to hybrids in Scrophularia is available. Goddijn and 

 Goethart 1 report that S. Neesii Wirtg. X &> vernalis L. is a 

 unified, stable, intermediate type and that the reciprocal is of 

 a similar character. 



The behavior of the original stock, and the facts of fertiliza- 

 tion, yield nothing suggestive of parthenogenesis, and the de- 

 rivatives may be taken to be produced by a typical fertiliza- 

 tion. No cytological examination has yet been made for the 

 purpose of ascertaining possible differences induced in the 

 chromosomes. 



This discussion may be fittingly brought to an end by a 

 brief reconsideration of the salient ideas which have been 

 touched upon. The point of view taken throughout all of the 

 work which has been described is one in which the conception 

 of a theoretical or idealized germ-plasm has been relegated to 

 secondary position, and attention has been concentrated upon 

 the concrete germ-plasm of the higher plants. This physical 

 basis of heredity is seen to present two distinct phases. In 

 one it takes the form of a meristem or embryonic tract of 

 highly distended cells in which auxesis and division are both 

 rapid and the elements which are separated from it pass by 

 differentiations into the permanent tissues of the soma. En- 

 vironic agencies affect only the development of the somatic 

 cells which are being formed from the meristem, and the ex- 



1 Ein kiinstlich erzeugtor Bastard Scrophularia Neesii Wirtg. X 8. vernalis 

 L. Van's Rijks Herb., Mededeel. 1913 1 *: 1-9. 1913. 



