AGRICULTURAL METEOROLOGY. 123 
day when the flower opens and closes should be marked, at the spring 
and autumn equinoxes, and the summer solstice. 
Observations relative to the vegetable kingdom may be taken from 
two aspects, the diurnal and the annual periods. The first is the return 
of the hour at which certain flowers open, atid these hours are fixed, 
being always similar in like species; the second, or annual period, is 
that which is comprised between the two successive returns of the 
leaves, flowers, and fruits. The application which may be derived from 
acquaintance with thése phenomena is of the highest importance, not 
only in agriculture, but also in meteorology and botanical geography. 
__ In pursuing the observations, the principal object should be to make 
them comparable, so that those of one’country may be contrasted with 
those of another. The chief point consists, then, in the choice of spe- 
cies and the,identity of comparative coudition, and not in the number 
subjected to examination. For attaining this object the following in- 
structions have been drawn up by Quetelet: 
1. Observations jor the annual period.—tn these investigations annual 
plants must be discarded, for they often come up at various periods, 
according to the time when they were sown; therefore the®indications 
furnished by them would not be comparable.* The same advice would 
also apply to biennials, because they come up slowly and at different 
times in autumn or spring. The only exceptions admitted are, of the 
autumn cerealia, rye, wheat, and winter barley, which are sown about 
the same time, and the phenomena of whese vegetation and flowering 
form a very important part in annual observations, because they relate 
to plants so extensively cultivated. The period of their being sown and 
that of the appearance of the ear should be noted. 
Plants for examination should be woody, or perennial ; the first are 
especially important, because taney are more subjected to the double 
combination of atmosplericaud terrestrial modifications; and also because 
they are better adapted than perennials for observations on foliation. 
It is important that plants for daily observation should have been 
planted at least a year; for vegetables transplanted in spring present 
too much uncertainty in their periods of foliation and flowering, these 
periods being subordinate to the formation of the roots. In selecting 
plants, those which flower through the entite year should be avoided, 
because they have no determined periods, such as the dandelion, chick- 
weed, and common groundsel. All those plants which yield varieties 
by cultivation should be avoided, as the rose and Tulipa Gesneriana, 
and the pear, cherry, and large-leaved lime-trees. Experience shows 
that among varieties produced trom seed-beds, Some flower fifteen days 
before others. To arrive at the comparative value of the flowering of 
these plants, it would be necessary to observe everywhere the same 
variety, and this is often impossible. Such plants as are of nearly 
allied species and difficult to distinguish should also be avoided. With- 
out attention to this, observers might be employing different species, 
which would destroy the comparative value of their operations. Finally, 
all flowers should be discarded whose estivation does not permit an 
accurate noting of the exact moment of expansion; such are the Caly- 
canthus, Illecebrum, Aquilegia, &e. 
. The periods at which rye, barley, and winter whéat come into ear 
should be carefully noted, this point being of great importance in agri- 
culture. In the district of Tourney, a farmer’s axiom is that “April is 
*M. Bergsma, president of the Horticultural Society of Utrecht, has, however, truly 
remarked that annuals might be usefully employed, provided precautions be taken to 
Use in every case the same seeds, and to sow them on the same days. , 
