MISSOURI BOTANICAL GARDEN BULLETIN 47 
18 years before, and which during this period had been ex- 
posed to a winter temperature of from 60 to 70 degrees below 
zero. Twenty-three years after these seeds were harvested some 
of them germinated, and this demonstration of the ability 
of seed to withstand low temperature was cited as one which 
would not likely be again repeated. Since that time seeds 
have been exposed to the temperature of liquid hydrogen 
(-250°C.) without deleterious results. Some contend that 
this proves the seed must necessarily be in a state of static 
equilibrium, since all chemical change must be in abeyance 
with such extreme cold. On the other hand, it is believed 
by many that any change would only be indefinitely retarded 
by the low temperature. 
Plants resort to various expedients to prevent their means 
of perpetuation through seed being destroyed by heat or 
drought or excessive moisture. As a general rule, the thinner 
and more permeable the seed-coat the shorter-lived the seed, 
although sometimes the seed-coat may be relatively thin and 
yet quite impervious to moisture, as in the case of the garden 
pea. Again, the long life of the seed may be due to the 
excessively hard or the abnormally thickened seed-coat, and 
germination may not take place for several years after the 
seed has been exposed to favorable conditions. To the farmer 
or gardener delayed germination is a nuisance, since he de- 
sires all seed to germinate promptly and those of the same 
kind to appear at approximately the same time. Clover is a 
good example of a plant which produces seed with coats of 
varying thickness, so that from a single plant the so-called 
‘‘hard’’ seed may germinate weeks or even months after the 
others. At one time a machine was devised which, by means 
of an air blast, forced the clover seed against rough iron 
plates, and these, by scratching the seed-coats, rendered them 
all equally permeable to moisture, and germination was more 
or less simultaneous. Still another method has been to sub- 
merge hard-coated seeds in strong acid, certain kinds being 
capable of standing this treatment for several hours without 
injury. Germination is thus secured within a reasonable 
length of time instead of requiring years. 
An interesting instance of the adaptability of plants to 
meet special conditions is found in Nelumbium speciosum, the 
sacred lily of India, the seed of which, if sown as soon as 
ripe, germinate under water in less than a month. Should 
