263 



Some fiii'tlier experiments l)y Pno-noul (1R70, p. 4S()) on the beet 

 as grown in darkness and in sunshine shows that the former were 

 exceptional!}^ rich in alkali, ash, and especially the nitrates. This 

 is explained as above, viz: The nitrates Avill 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. 



P'rom 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 w'ork occnr 

 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 aronnd 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 b}' Cailletet that green light has no power to bring 

 about the decomposition of carbonic acid. 



In the Annuaire for 1883 Marie-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 the climate as such or from the ravages of insects or 

 fungi, it is necessar}' 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 

 Marie- Davy (pp. 244-285 of his ^Vnnuaire 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 Marie-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 i)redict the time of harvest, the quantity 

 and quality of the cro]), and the range of uncertainty. To this end 

 it is, of course, imderstood that corresponding elaborate tables of 



