1 8 Plant Genetics 



character of it any more than a rubber hot-water bag, 

 although capable of assuming a variety of shapes, can 

 affect the character of the water it contains (Walter 6). 



Opponents of Weismann object to any such view 

 of the complete isolation of germ plasm. Studies of 

 cell Hneage in animals have shown that germ cells are 

 set apart very early in the development of the individual, 

 and that they certainly are not derived from distinctly 

 somatic cells. No such statement, however, can be 

 made in reference to plants. Germ cells in plants are 

 derived from epidermal or hypodermal cells, which 

 previously were distinctly somatic; and furthermore 

 germ cells have been induced by experiment to form from 

 almost any living tissue which is as distinctly somatic 

 as any plant tissue can be. 



Another objection to Weismann's view is that every 

 organism is a physiological as well as a morphological 

 unity, and that cells completely insulated in such a 

 unity would be impossible. Cytologists also have come 

 to believe that there are protoplasmic connections 

 between adjacent cells in practically all plant tissues, and 

 in general physiology tends to confirm this. All of this 

 means a growing belief that the somatoplasm can affect 

 the germ plasm. 



The reply of the Weismannians is that even though 

 somatoplasm can affect germ plasm in this general phys- 

 iological way, this is a very different thing from the in- 

 inheritance of some definite acquired character. To be 

 inherited such a character would have to be exactly re- 

 developed in the germ plasm, and the influence referred 

 to caimot be so specific as that. This of course is a 

 theoretical answer and the question can only be decided 



