342 BOTANICAL GAZETTE [MAY 
plants. The evidence indicates that this is a case of maternal 
inheritance. In no case has pollen from the affected plants of this 
strain produced any visible effect when used in crosses on green 
plants, either in the first or succeeding generations. 
It is clearly evident from these cases that the inheritance of 
chlorophyll variations can hardly be accounted for on the basis 
of a single explanation. There are widely different categories 
which at present seem to be entirely distinct. In the case of the 
Mendelian behavior, the explanations offered are the same as for 
any other character behaving in a similar manner, although other 
cytoplasmic organs having a certain degree of individuality are 
apparently more directly involved in bringing the characters to 
expression. In this category characters expressed by intracellular 
organs are apparently under the control of nuclear factors, just as 
are other Mendelian characters expressed by tissues and multi- 
cellular organs. The hypotheses advanced to account for the non- 
Mendelian behavior of similar characters assume that the plastids 
themselves are permanent cell organs capable of transmitting 
certain characteristics, and are not controlled by nuclear factors; 
and furthermore, that in certain cases plastids are transmitted to 
succeeding generations by both parents, and in other cases only 
by the female parent. It must be admitted that such explanations 
are highly speculative, in view of the number of cytological observa- 
tions which have so far been made. 
METHODS AND TECHNIQUE 
The general procedure followed has been to examine the material 
in the living condition, the observations thus made being supple- 
mented by a study of fixed and stained preparations. It was found 
that meristematic tissue, including apical meristems and young 
leaf tips of germinating seeds, could readily be studied in this way. 
It was necessary in the case of older tissues to remove first the 
epidermal layer of cells before examining the mesophyll cells 
beneath. A solution of cane sugar of 7.5—10 per cent concentration 
was found to be a favorable medium in which to examine fresh 
material. Cells which are protected by one or two cell layers oF 
by epidermal cells will remain living for a considerable period of 
