OF FOREST-TREES. 



19 



At specimen sationis, et insitionis origo 

 Ipsa fuit rerum primum Natura creatrix : 

 Arboribus quoniam baccse, glandesque caducae 

 Tempestiva dabant puUorum examina subter. 



LUCRET. l.v. 



CHAP. I. 



Nature herself, who all created first. 

 Invented sowing, and the wild plants nurst : 

 When mast and berries from the trees did drop. 

 Succeeded under by a numerous crop. 



Yet this is to be considered, that if the place you sow in be too cold for 

 an autumnal semination, your acorns, mast, and other seeds may be 



" dence, with the most consummate wisdom, keeps up the necessary rotation of 

 " things." Georg. Essays, p. 332. 



So far I had considered this putrid nutriment as absorbed by the roots of plants ; but the . 

 ingenious experiments of Dr. Priestley refer to the absorption of the putrid air by the 

 leaves of plants. That I had also i-emarked in a variety of places. "Hitherto I have 

 " considered plants as nourished by their roots ; I shall now take a view of them as 

 " nourished by their leaves. An attention to this part of the vegetable system is 

 " essentially necessary to the rational farmer. Vegetables that have a succulent leaf, such 



as vetches, pease, beans, and buck-wheat, draw a great part of their nourishment from 

 " the air, and on that account impoverish the soil less than wheat, oats, barley, or rye, 

 " the leaves of which are of a firmer texture. Rape and hemp are oU-bearing plants, and 



consequently impoverishers of the soil ; but the former less so than the latter, owing to 

 " the greater succulency of its leaf. The leaves of all kinds of grain are succulent for a 

 " time, during which period the plants take little from the earth ; but as soon as the ear 

 " begins to be formed, they lose their softness and diminish in their attractive power. The 

 " radical fibres are then more vigorously employed in extracting the oily particles of 

 " the earth for the nourishment of the seed. Such, I apprehend, is the course of 

 " nature." Ibid. p. 25. 



" The air contains, especially during the summer months, all the principles of vegetation ; 

 "oil (phlogiston) for the perfect food, water to dilute it, and salts to assimilate it. These 

 " are greedily absorbed by the vessels of the leaves and bark, and conveyed to the inner- 

 " most parts of the plant for its growth and fructification." Ibid. p. 64. 



" In order that we may have a distinct view of the motion of the sap, it will be neces- 

 " sary to reflect, that the root, stem, branches, and leaves are constructed in the same 

 " manner. Sallows, willows, vines, and most shrubs, will grow in an inverted state, with 

 " their tops downward in the earth. Dr. Bradley describes the manner of inverting a 

 " young cherry-tree, the roots of which will put forth leaves, and the branches become 

 " roots. Hence it is obvious that the nutrl'tivie matter may be conveyed as well by the 

 " leaves as the toots, their vascular structure being the very same." Ibid. p. 79« 



K 2 



