356 BOTANICAL GAZETTE [MAY 
known cases of plastid inheritance do not appear to be in the same 
category, and as yet have not been explained by a common well 
substantiated hypothesis. 
Examples of chlorophyll characters which are inherited as 
Mendelian recessives have been described by numerous workers. 
Among the researches dealing with such characters may be men- 
tioned those of Emerson and Linpstrom in maize, and those of 
Baur, KreEss_inc, TJEBBES and KoormmaAn, Miyazawa, CoRRENS, 
and ALLARD on a number of other plants. The hypothesis held to 
account for the transmission of these characters is the same as that 
upon which the behavior of other Mendelian characters has been 
explained. Although the character in question is expressed in the 
plastids, the cell activities which result in the appearance of the 
character seem to be under the control of nuclear factors. If the 
character is thus under the control of a nuclear factor, it is neverthe- 
less of importance to determine whether plastids are present in col- 
orless cells as well as in normal ones; and also to determine to what 
extent the plastid is a permanent cell organ multiplying by division, 
especially if it is desired to gain insight into the process through 
which the character is brought to expression. 
Mites (47), in a cytological investigation of as seedlings 
in maize, reported that in the pure white plants no plastids could 
be differentiated. This does not at all correspond with the findings 
of the writer. Partially matured plastids are present in all of the 
mesophyll tissue of the plant, and in certain regions a limited 
number of mature functional plastids are present in some cells. 
Plastids, therefore, are not entirely absent, but their development 
is permanently retarded in the white seedlings. In the virescent 
plants the normal development of the plastids is interfered with 
only in the seedling stage. 
Other chlorophyll types in maize which are Mendelian appear 
to be normal in the seedling stage, but the character appears in 
the plant as it approaches maturity. In fact there are known in 
maize markedly different chlorophyll types, and it seems certain 
that additional ones will be described. These cases are of interest 
cytologically in that apparently there is a wide variation in the 
condition of the plastids in the affected plants. 
