The whole of this subject appears to be debateable ground between the physiologists and chemists: the one considering the change of starch into sugar as the result of the vital action of the seed; the other affirming that the growth of the germ is in no way necessary to the result, and is to be considered as a mere indication of the due degree of change being effected in the organic matter, or, in other words, that when the organized parts exhibit a certain degree of developement, then the inorganic matter is most completely changed. All growth beyond this is injurious, as leading to a consumption of the inorganic matter. All less than this is not otherwise disadvantageous, than as an indication that the inorganic matter is not duly changed. This change, it is farther affirmed, so far from depending upon vegetable life, can be wrought on the matter of the seed after it is even reduced to powder, or is separated in the form of starch. At all events, it must be admitted as a beautiful arrangement in nature, that the same agents which urge on the developement of the organized parts, should, at the same time, assist in preparing food for their support. From this subject Davy is very naturally led to the consideration of the ravages inflicted upon the infant plant by insects; the saccharine matter in the cotyledons at the time of their change into seed-leaves, rendering them exceedingly liable to such attacks. He appears to have bestowed much attention on the turnip-fly, a colyopterous insect, which fixes itself upon the seed-leaves of the turnip at the time that they are beginning to perform their functions. He relates the several remedies which have been proposed for this evil; and from letters which have been put in my possession, addressed to Dr. Cartwright as early as the year 1804, he appears to have been engaged with that gentleman in experiments made by sprinkling the young plants with lime and urine. After alluding to the parasitical plants of different species, which attach themselves to trees and shrubs, feed on their juices, destroy their health, and finally their life, for which, at present, there does not exist any remedy, he thus concludes his lecture: "To enumerate all the animal destroyers, and tyrants of the vegetable kingdom, would be to give a catalogue of the greater number of the classes in Zoology. Every species of plant almost is the peculiar resting-place, or dominion, of some insect tribe; and from the locust, the caterpillar, and snail, to the minute aphis, a wonderful variety of the inferior insects are nourished, and live by their ravages upon the vegetable world. "The Hessian fly, still more destructive to wheat than the one which ravages the turnip plant, has in some seasons threatened the United States with a famine. And the French government is at this time[108] issuing decrees with a view to occasion the destruction of the larvæ of the grasshopper. [108] January 1813.