AGRICULTURAL CHEMISTRY AND GEOLOGY. 209 



stances, it was found that the cutting off of the chemical rays favors the first germination of 

 the seed ; and this appears to be the principal, if not the only, advantage of the darkness 

 obtained by burying the seeds in the soil. 



The development of roots requires also the absence of the chemical ray, but is rather 

 favored than otherwise by heat and luminosity. The first development of the plumule also 

 proceeds best under the same circumstances. Yet these are not the conditions which produce 

 a healthy plant; they cause too rapid and succulent a growth. When the plant is fairly 

 established, those radiations which are, comparatively speaking, devoid of light, but replete 

 with chemical power, seem the most suited to it. The points in common between the differ- 

 ent actions of the solar radiations on wheat and on peas are, that in both cases the cutting 

 off of the chemical ray facilitates the process of early germination ; and that both in reference 

 to the protrusion of the radicles and the evolution of the plume, obscurity causes an unna- 

 turally tall growth and poor development of leaves, and the yellow ray exerts a repellant 

 influence upon the roots, giving the wheat a downward and the pea-roots a lateral impulse. 

 A comparison of the results obtained by means of the yellow, of the obscured colorless, and 

 the obscured yellow glasses, showed that the yellow ray has a specific action in many respects, 

 but not of the character which has sometimes been ascribed to it. The diversity of effect of 

 the same ray upon the two plants was well exhibited by what took place under the colorless 

 and red glasses. Under the former there grew a tall and vigorous crop of wheat-plants, with 

 a mere matting of stunted roots from the peas, while under the latter a thick crop of green 

 and spreading plants arose from the germinating peas, but the wheat were few and straggling, 

 and unhealthy in appearance. Seeds of the wheat and the pea were placed in jars, con- 

 taining respectively carbonic acid gas, hydrogen from which every trace of oxygen was 

 removed by pyrogallate of potash, common air from which carbonic acid was removed by 

 caustic alkali, and normal atmospheric air. These merely corroborated the opinion generally 

 entertained, that oxygen is absolutely requisite for instituting the first change in the coty- 

 ledons of the seed. Peas and wheat were also grown in oxygen gas, under the colorless and 

 colored bell-jars. They grew and appeared to flourish best under the chemical influences 

 of the blue glass. 



The Grittiness of Pears. 



The grittiness of pears greatly diminishes their value as a dessert. The proximate cause 

 is known to be the deposit of hard matter in the pulpy cells, analagous to that which gives 

 the bony texture to the stone of plums, cherries, &c. In stone fruits the gritty matter is 

 collected, and forms the pit or stone ; but in the pear there is no part exclusively appropriated 

 for the grit, which is found sometimes in large or small masses throughout the pulp. 



The cause of this grittiness is unknown, but the accumulation of it may be arrested or 

 diminished by sheltering the fruit from the cold rain which may fall during its growth, and 

 arrest the free circulation of the sap. This hypothesis was suggested by M. Delaville, a 

 French gardener, who remarks that the sorts which are most subject to spotting and grit- 

 tiness are those which have the finest skin. 



The manner in which M. Delaville protects his pears is as follows: As soon as the fruit is 

 completely set, he encloses each cluster in a cornet of paper, fixed to the top of the stalk by 

 a piece of rush, (bast.) This cornet must be sufficiently large to guard the fruit from all 

 exterior injuries. The cornet should be very wide, and the small end placed upwards, so as 

 to leave nothing uncovered except the bottom of the fruit-stalk. But this protection is 

 unnecessary where the fruit is trained against a wall. About a fortnight before gathering, 

 the cornet should be removed, in order to give the fruit color and to complete the ripening. 



At the exhibition of the Imperial Horticultural Society of Paris, some St. Germain pears 

 were exhibited, part of which were full of spots and grittiness, while others were fine and 

 pulpy. Both samples were from one tree, but the fine ones were protected in the manner 

 above described. — Phil. Florist. 



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