No. 511] NOTES AND LITERATURE 



439 



Crosses made between flowers on pure white branches and 

 other flowers on ordinary green plants gave thirty-nine green 

 seedlings and seven green-white marbled plants. These crosses 

 were made both ways, but only one seed, resulting in a green 

 plant, was raised from the cross of green (g) on white ($). 



Several crosses made both ways between white margined plants 

 and ordinary green plants gave 199 pure green, 41 green-white 

 marbled, and 4 pure white seedlings. Crosses between white 

 margined and pure white branches gave all pure white seedlings. 

 Evidently, white branches and white margined branches produce 

 only white gametes, while green branches or green plants produce 

 only green gametes. 



Of the green-white marbled seedlings — that is, green and 

 white spotted, some formed only white leaves and died when the 

 spotted cotyledons ceased to function. 



A second class formed only green leaves and became ordinary 

 green plants when the spotted cotyledons dropped off. Their 

 seedlings, about 50 in number, were all ordinary green plants. 



A third class grew stems that were white on some sides and 

 green on others. On such stems leaves attached to white surface 

 were wholly white, and those attached to green surface were 

 wholly green. Leaves attached on the line of union between 

 green and white were correspondingly green and white. 

 Branches which grew from the axils of the leaves behaved in 

 exactly the same way as the leaves in regard to the green and 

 white color. 



These facts render it clear that the marbled seedling consists 

 of two kinds of tissue— green and white. The descendants of 

 white cells are white and those of green cells are green. A green 

 and white seedling or branch may become either green or white 

 by the growing point becoming overcapped by the one or the 

 other kind of tissue. Of 23 marbled plants observed 20 became 

 green and two white in this manner. 



But the development of a marbled branch or plant may proceed 

 in a different manner and one which clears up the difficulty con- 

 cerning the nature and hereditary relations of the white marbled 

 plants. In a marbled stem the line of contact between the two 

 kinds of tissue may extend radially inward, or the white 

 tissue may extend in a thin layer some distance over the green. 

 A leaf rising centrally on a line of contact extending radially 

 inward will be half white and half green ; but a bud originating 



