174 
ON DESTRUCTION OF INSECTS BY PYRET1IRITM. 
it. The first sown, on September 15, 1856, produced only a few shoots. A'great point 
was to ascertain whether the plant was an annual or perennial. In order to detennine 
this, several of the procured plants passed through the winter of 1856-57, and sustained 
from 8 to 12 degrees of cold without appearing to suffer. 
The seeds gathered from this first culture were sown in February, 1858. In May, we 
communicated our experiments, and the success that had crowned them, to Messrs. 
Decaisne, Neumann, and Pepin. These gentlemen then examined the plant botanically, 
and their opinions are as follows:—(Here follows a botanical description of the genus 
Py rethrum, and of the particular plant just referred to, from which it appears that the 
present species has not hitherto been described; hence M. Duchartre has named it Pyre- 
thrum Willemoti.) 
Culture and Gathering .—The Pyrethrum, though a native of the Caucasus, where 
it grows abundantly and at a slight elevation above the level of the sea, under a latitude 
warmer than that of Paris, succeeds very well on good soil in France. It is very hardy, 
and can sustain without hazard the severe winter there. A few years’ experience has 
taught the writer that it is little sensible to cold, and that it needs no shelter during the 
winter. It has been asserted that the kindred species which also grow in the Caucasus 
have rather suffered than benefited by the shelter given to them. The soil best adapted 
to the culture of the plant is a pure earth somewhat siliceous and dry. Moisture and the 
presence of dung is injurious, the plant being extremely sensitive to a mass of water, and 
would in such case immediately perish. A southern aspect is the most favourable. The 
best time for putting the seed in the ground is from March to April. It can be done 
even in the month of February if the weather will permit it. After the soil has been 
prepared and the seeds are sown, they are covered by a stratum of soil mixed with some 
vegetable mould, and the roller is slightly applied to it. Every five or six days the 
watering is to be renewed in order to facilitate the germination. 
At the end of about thirty or forty days the young plants make their appearance, and 
as soon as they have gained strength enough they are transplanted. Three months 
after they are transplanted again at wider distances, according to their strength, each 
time being of course watered, but only moderately. 
The blossoming commences in the second year towards the end of May, and continues 
to the end of September. Within that period the heads from which the powder is made 
must be gathered. The most favourable time for gathering seems to be when the heads 
are about to open,—that is, when the florets of the circumference are yet standing 
erect. In this state the fecundation takes place, and the essential oil contained in the 
heads has reached its highest state of development. The stalks and leaves, through 
having the properties in a less degree, may be used also for making powder, but they 
must be mixed w'ith the flowers in the proportion of a third of their weight. The pow¬ 
der thus obtained will perfectly answer the destruction of insects. Towards the end of 
September, at which time the blossoming has ceased, the stalks are cut at about four in¬ 
ches from the ground. As the flowers are cut they are dried in a granary or shed, great 
care, however, being taken not to expose them to moisture or to the rays of the sun. 
When completely dried the flowers are to be hermetically closed up in sacks, so as to 
prevent too early pulverization. In pulverizing them it is better not to take a larger 
quantity than the w'ants of the moment may require. The volatilization, which is of 
course more rapid in the powdered form than in flowers, will thus be avoided. It has 
been suggested that the drying of the flowers for making the powder might be effected 
on sheet-iron plates, like tea-leaves are dried in China, but this operation is most injuri¬ 
ous to the plant, dissipating the essential oil. 
Pulverization .-'—Among the numerous methods which we have tried in order to sim¬ 
plify the pulverization of the dried flowers, that which appears the best is to pound the 
flowers in a mortar. The mortar should be covered with a piece of leather, through 
which the pestle moves, adjusting it in such a way as to prevent any contact from with¬ 
out, as is usually done in pulverizing drugs in a laboratory. The quantity to be pulverized 
should not exceed a pound at a time, thus avoiding too high a degree of heat, which would 
be injurious to the quality of the powder. The pulverization being deemed sufficient, 
the substance is sifted through a silk sieve, and the residue, with a new addition of 
flowers, is put into the mortar and pulverized again. 
This method of preparation is so simple as to be within the reach of all; the pulveri¬ 
zation by steam is more rapid and effectual, but necessarily more expensive. The best 
