154 PHYSICAL BASIS OF HEREDITY 



case. The new moss-plant is therefore 2N (or diploid) 

 instead of being IN, as in the normal mode of propaga- 

 tion. Since no reduction has taken place into male- and 

 female-producing individuals, it would seem possible that 

 such a plant might produce either or both sexes. Such 

 is the case, for when the 2N moss plant produces its 

 ^* flowers'' some contain archegonia, others spermato- 

 gonia (with their contained germ-cells) and other flowers 

 contain both. The hermaphroditism here produced would 

 seem to be the sum of both the contrasted elements. The 

 expectation from such a 2A^ plant would be that its germ- 

 cells {2N) would produce a 4iV sporophyte — unfortunately 

 the plants proved sterile. Imperfect germ-cells were 

 present incapable of fertilizing or of being fertilized, 

 so that it was not possible to perpetuate the 2N plant by 

 sexual reproduction. 



The results with the 2N plants derived from the regen- 

 erating sporophyte of the hermaphroditic species (Fig. 

 61) is different in one important respect. When, as 

 before, a diploid i2N) plant is obtained by regeneration 

 from the sporophyte it produces hermaphroditic flowers, 

 i.e., flowers containing both oogonia and spermatogonia, 

 and these are fertile. The sporophyte that they produce 

 is tetraploid {4tN), due to the union of a diploid anther- 

 ozooid with diploid egg. Regeneration from the tetraploid 

 sporophyte (42V) should produce fertile gametes, which 

 might give rise by their union to an octoploid sporophyte 

 (8iV) . So far the Mar^chals have not been able to produce 

 such plants, for although in a few cases the 4:N sporophyte 

 regenerated it failed to produce flowers. 



The difference then between the results from mosses 

 with separate sexes and mosses that are hermaphrodite is 

 that the 2N plant of a race with separate sexes does not 

 form normal gametes, while a 2A^ plant of hermaphroditic 

 races forms fertile gametes. It may appear more or less 

 plausible that the failure of the former is due to failure 

 in the reduction of the spores into two alternative types, 



