3870 Stout: Bup-VARIATION IN PELARGONIUM 
In the light of Baur’s anatomical studies this sort of bud-varia- 
tion is readily understood as due to a mechanical readjustment of 
the two kinds of cells already in the growing points. This par- 
ticular type involves more extensive rearrangement than the 
cases where pure green or pure white branches are produced by 
the development of a bud containing only one kind of cells to the 
exclusion of the other. For the development of a branch re- 
versing the position of the two kinds of cells as described above 
there must be a breaking out of the enclosed green cells in the 
growing point and a growth of both green and white cells in such 
a manner that the green cells surround the white cells. It may be 
that in this case the green cells break forth at two separate points 
not far distant and that in further growth they meet, enclosing 
the white cells. 
On the main portion of the plant here shown, the mature 
leaves possess over their whole surfaces two peripheral cell-layers 
that are white. To maintain this relationship the cell divisions 
which give rise to these layers must occur only in planes which are 
at right angles to the surface of the leaf, The outer layers do not 
contribute to the vascular tissues and the inner green tissue does 
not form epidermis, a fact clearly shown by Baur. In the sporting 
branch, however, the green cells get to the surface and form the 
epidermis as well as some of the mesophyl and vascular tissue, 
while the white cells cease to form epidermis and now contribute 
only to the inner tissues. The cells preserve the green and white 
character of their chromatophores but take on different structures 
or different functions according to position and environment. © 
In his interesting report of results of anatomical and hereditary 
studies of variegated varieties of Pelargonium, Baur was not 
especially concerned with the evidence of interaction between the 
two kinds of cells, the white and the green, where both exist in 
the same leaf. His photographs, however, show the same sort of 
difference which have appeared so strikingly in the case here under 
consideration. 
The marked differences between the two kinds of leaves pro- 
duced on this plant (PLATE 20) make it clear that the outer layers 
largely determine the size of the leaves and the depth of the lobing- 
When the green is outside the leaf is larger, more deeply lobed and 
