263 
Some further experiments by Pagnoul (1879, p. 486) on the beet 
as grown in darkness and in sunshine shows that the former were 
exceptionally rich in alkali, ash, and especially the nitrates. This 
is explained as above, viz: The nitrates will not decompose within 
the plant except under the influence of sunshine; if the plant is 
kept in darkness it stores up the nitrates within itself without having 
the power of utilizing its own nitrogen, so that the substances in the 
formation of which this nitrogen ought to be of assistance can not be 
formed. 
From this one must conclude that years that are bad for the beet- 
sugar crop are so not only because of unfavorable temperatures and 
humidities but above all because of a defect in the insolation. Lively 
complaints have been made of the quantity of nitrates in certain 
harvests; now these salts that accumulate in the molasses and in 
the inferior products and augment the difficulty of the work occur 
often in beets cultivated upon a soil that has never received a trace 
of nitrates as a fertilizer. It is therefore not to the abuse of nitrates 
as a fertilizer that we ought to attribute their presence, but rather 
to a too cloudy sky. 
We know that the neighborhood of large trees is injurious to the 
vegetation around them. Ordinarily we attribute this injurious 
influence to their roots. It would perhaps be more exact to attribute 
it to the shade that they cast, and the more so because it has been 
demonstrated by Cailletet that green light has no power to bring 
about the decomposition of carbonic acid. 
In the Annuaire for 1883 Marié-Davy studies the influence of the 
date of sowing. In order to ascertain the best dates for sowing and 
trace out the various vicissitudes to which the crop is subject, whether 
resulting from tlie climate as such or from the ravages of insects or 
fungi, it is necessary to make a rather detailed study of the state of 
development of the plant under the assumption that the seeds were 
sown on successive dates—for instance, on a given series of successive 
week days. An elaborate study of this kind is given for wheat by 
Marié-Davy (pp. 244-285 of his Annuaire for 1883), from which the 
following tables have been extracted. In general the varieties of 
wheat cultivated in the south of Europe are more sensitive to cold 
than those of the north, but the studies of Marié-Davy for the latitude 
Montsouris, when paralleled by similar studies for localities in the 
United States, can but be of the greatest value both to the farmers 
and the statisticians of this country. The study of such tables will 
enable one to very closely predict the time of harvest, the quantity 
and quality of the crop, and the range of uncertainty. To this end 
it is, of course, understood that corresponding elaborate tables of 
