[Vor. 4 
210 ANNALS OF THE MISSOURI BOTANICAL GARDEN 
simple constituent of the medium to be destroyed or used up 
in the metabolism of the organism. The organism should 
furthermore not be restricted to the use of a single compound 
as a source of food, but substitutions could be made. The 
metabolism would furthermore not be governed to the same 
extent nor in the same manner as are single chemical reac- 
tions, though it would undoubtedly be influenced by physio- 
logical relations much the same as are other organisms. 
New AND RECENTLY Descrisep Mosaic DISEASES 
Although cucumber mosaic has been known for several 
years, its economic importance has not been appreciated until 
recently. Since the prevalence of the disease is only par- 
tially known, it is difficult to estimate the annual loss in- 
volved, but it undoubtedly approximates a million dollars an- 
nually. It is reported from an area bounded by Minnesota, 
Colorado, Mississippi, Virginia, and New York. The foliage 
of diseased plants always assumes the curled or crinkled and 
mottled appearance characteristic of mosaic diseases, while 
the fruit may remain small and cone-shaped, or become ex- 
tremely ‘‘warted’’ and mottled, or only mottled and по! 
greatly deformed as shown in pl. 16, fig. 1. 
The new mosaic disease of peanuts has recently been de- 
scribed by McClintock (’17). But a single plant was found, 
and all inoculation experiments gave negative results. On 
account of shortage of material with which to carry on ex- 
tensive inoculation experiments, it was impossible to establish 
definitely the identity of the disease. 
A disease appearing spontaneously on avocado plants! 
grown in the greenhouse for experimental purposes, showed 
all the characteristics of mosaic diseases. So far as can be 
ascertained by the writer, no observations of this kind have 
ever been made. The plants were grown in a room together 
with diseased tobacco plants, and it is therefore impossible 
to state whether the disease was contracted from the tobacco 
or whether it is distinctive of the avocado. The plants are 
1 The seeds for these Ба ди obtained from Santa Anna, California, 
through the courtesy of W. 5. Ree 
