158 MISSOURI BOTANICAL GARDEN BULLETIN 
For instance, we know that iron and magnesium salts are 
necessary to the formation of chlorophyll, and that without 
these chemicals plants will become colorless and may event- 
ually die. Again, some types of variegation take place only 
in the sunlight, and the mere transfer of the plant to a shady 
place enables the new leaves to be of the normal green color. 
Injuries likewise produce chlorosis of different types, and 
instances of bleaching in cabbage, parsley, and similar gar- 
den crops which have been nipped by an early frost are com- 
mon. Damage induced by insects or unfavorable conditions 
of the soil may also cause leaves and tender stems to lose 
their green color, although yellowing due to injury, lack of 
food, etc., is in general very different from what we ordinarily 
term variegation or true chlorosis. 
Baur, a German botanist, has obtained some interesting 
results by grafting scions from certain variegated plants on 
stocks of normally green varieties of the same species. He 
demonstrated that in some cases stocks thus grafted would 
later produce variegated foliage, and he consequently be- 
lieved that the cause of the variegation in the scion is trans- 
mitted to the stock. 
There seem to be two distinct forms of chlorosis, however, 
the one, infectious, and the other, non-infectious, since with 
some plants it is impossible to produce any effect on the 
stock, even though it be grafted with a variegated variety, 
and one plant ouynae japonicus) was found to possess 
both the infectious and non-infectious forms. It is likewise 
true that some varieties are immune to the infectious chlo- 
rosis which is readily transferred to other closely related 
forms. Among the plants which show what is supposed to 
be non-infectious variegation are Bougainvillaea glabra 
Sanderiana, Fittonia argyroneura, the silver-banded gera- 
nium (Pelargonium hortorum var. albo-marginatum) , 
varieties of elephant’s ears (Caladium), which show some 
of the most remarkable instances of absence of chlorophyll, 
as well as the numerous striped and banded grasses. 
An interesting example of what is apparently an infec- 
tious chlorosis may be seen in the whitened tips of the club 
moss (Selaginella Kraussiana) growing in the fern house at 
the Garden. Such variegated forms are always propagated 
by cuttings, but are never inherited through the seeds. This 
is not true, however, of the variegation due to non-infectious 
chlorosis, which is tuated through the seed. If the 
juice of a plant, like tobacco, having an infectious chlorosis 
comes in contact with a wound on any part of a normal plant 
of the same kind, the latter may show symptoms of the dis- 
