30 Principles of Plant Culture. 
much more convenient. This useful device consists of two 
circular pieces of moderately thick cloth, a table plate that 
is not warped, and a pane of glass large enough to cover the 
plate. The cloths are dipped in water, wrung out a little 
until moderately wet, spread over the bottom of the plate 
as shown, and the seeds to be tested are placed between 
them. It is well to use a hundred or more seeds of each 
sample, as a larger number will show the per cent. of vitality 
more accurately than a smaller one, and the lot should 
always be well mixed before taking the sample. The plate 
should be kept covered with the glass to prevent evapora- 
tion from the cloth, and it may be placed in any room of 
comfortable living temperature. The seeds should be fre- 
quently examined, and may be removed as they sprout, 
when by subtracting the number that fail to sprout from 
the number put in, the per cent. of vitality may be readily 
computed. The cloths should be placed in boiling water a 
few minutes before using them for a second test, to destroy 
any spores or mycelia of mold with which they may have 
become infected. 
40. The Time Required for Germination varies 
greatly in different kinds of seeds. In lettuce seed, the tiny 
white shoot often breaks through the seed-case within 
twenty-four bours from planting, while celery seed requires 
several days to germinate to this extent. The sceds of 
many plants will not germinate the same season they are 
formed even if planted under the most favorable conditions. 
Individual seeds of the same kind and of the same sample 
often vary greatly in the time required for germination. 
Even in seeds that germinate soonest, as lettuce and radish, 
some individuals will not germinate until several days after 
