LEAVES AND THEIR USES.

Thames Star, Volume XII, Issue 3885, 11 June 1881, Page 4

LEAVES AND THEIR USES.

At a'reident meeting of the Opotiki "•: Farmers' Club, Mr, J. P., Parkinsoniread. " "the following.paper on ; \\ Leaves and their uses ":—Leaves of trees and other plants t- are £o> common to everyone that few

people 'give them a thought, they are . \ looked upon as the natural product of the plant, with do consideration of their uses.

We eat an apple, and are satisfied ; that v. the'tree has produced it, we cut a cabbage •*;' and, tear off/the coarse outside leaves as only fit for the dung heap, casting ; them /r-away as we would an old hat or pair of shoes, never bestowing a thought on their former service. Then we praise the • white hard heart of the cabbage or lettuce x::r-foflls'bel»uty arid crispness, and perhaps we may condescend to praise the soil in which it grew; while the real working

part.of..the plant is trodden unde"!' foot, U -the'•'tea£ that has protected and"supplied it with substance and flavour is thrown away. There are only two classes of leaves „,! fb jelQnging toSthe whole world'b^regeta- ' tion, and by the construction of them botanists know the nature or character of the plant, to „ which they belong. If we 'jpibtatt^e leaves of the cabbage tree, the liugar'cane, maize, and most gooseberries,' we find them all to be constructed in a similar : way, /They are jalt long, the midrib and veins leading direct from, base to f |p|iiit./!-T|iOße leaves belong to that felass < 'of plantsand trees whose growth proceeds from ,the centre or h'earc of the plant; r> this class is named by the botanists jjindogenons (meaning growing from the ij inside)^; The other class of leaves is very ■odiffereut, and by their construction is the nature of the plant to which they belong. To this class is given the name ofjefOgenous (or growing from the outside). Nearly all timber and fruit trees belong to this class, also most vegetables. -t l Now look at the. leaf of the grape, the

&i>j>U, . &%. pumpkin,. cucumber;, or of 1 .al'mosV, any tree. ; We find . it :has, a '\^'l strong frame of woody fibre, consisting of '.';i; mid-rib^ veins, and, veinlets, every plant , hating a different shaped leaf, but all . ; formed' -Ofr Ith'e* same principle. We will a' take the leaf of an apple tree for exami- : • nation, as that will answer for all of this class. The upper surface is a glossy green, the under is pale and dull; these two surfaces or skins are r called. . iJttpideriMis, whichis the name for all eiternal skin. .These surfaces are composed of ( „ fine tissue, perforated ,with< small; opening V' or pores, varying in different leaves from ]y ?0,p.0Q t0,.; 100,000 to: t the, square inch on the. under >side, but not so many ion the 1 a upper side of the leafi These opecings # are breathing pores called etomata; and ;•; are surrounded by guard cells so delicate V, that.they will contract or dilate according to,' Jthe .state, of the .atmosphere, thus 'closfng'tW pores in dry; leather, and - opening them as circumstances,' admit. ' TKe(i^tferior,;of j the ;leaf; ii filled with Vgrie^pufpV the granules of which caa *'*!6ril3f.be,.,seen .by the microscope^ which shows tliem to be composed of minute cells \ oontaining'a green fluid, called .chlorapnyl. This subsfanca,is colourless; in the first [J stpge of tfte plant,, but, a; ;few.' hours exposure tothe rays of the sun turns it „green ; if the leaf were kept from the light jfof,the sun, this substance would remain y' colourless,.. and the plant• vrould die. it Between these cells are open spaces called „ .intercellular spaces, these cells differ in '■ ■- the leaf. Underneath the'uppe'r skiri is a ■layer of long cells placed side by side, "<v beneath these is the softer tissue 'of its cells are hot:so regular; in position, being placed ao as to touch each votjher- at few points. These cells are "irregular caves or bags, containing minute granules oftiJhldrbphyHo which the green <colour of the. leaf is'due. The millions of grains contained in a single leaf are composed of a substance called protoplasm, 'and constitute the laboratory'of the leaf in which the changes are wroaght, •whereby the solutions derived from the Boil by the roots of the plants,, together with the gasses and beams of the sun obtained by the leaves, become solid subatance« such as woody fibre, fruit, &c: I We have now seen the place of the work! of assimilation, but how it is done is only guess work, but it is established as truth that these green granules do the work of preparing the material of which' the plant is oomposed, and that they may be so placed; as to receive the rays of the sun, and the elementary material necessary for their . .'support. We now can understand why the (rays of the sun, with plenty of light anaair,: are so necessary to the health of plants. (The whole of the atmosphere surrounding .being charged with carbon, is breathed by leaves (which are, the same to the plant as 'the lungs are to animals), and mixing in those chlorophyl cells with those fluid elementary substances taken from the earth by theroqts of the plant constitute the vascular tissue of which the plant is composed. Most people suppose the substance of trees and plants of every kind are.taken direct from the'foil, but inch does not appear', to be the caße, as the rootlets do not take up a particle of solid substance of any kind. All of the elementary substances required for plant food are taken up the plant to the' leavas in solution, all those giants of the forest, the oak, pine, and stately cedar, as well as the least shrub that grows, receive their-nutriment in the same way, thus receiving strength from the soil to assimilate the gases contained in the atmosphere into wood and fibre, forming material (cambium). This descends from the leaf after being prepared by the action of the rays of the,sun down the tree between the bark and the wood, and gradually hardens, each successive layer pressing harder. as it solidizes on the preceding one 1, thus forming wood (alburnum) or,other hard fibre. We are now led to conclude that the whole of the vegetable' kingdom is formed from the ■gents contained in the atmosphere, elaborated by the chlorophyl contained in tfie, leaves of the. "tree or plant of any kind, and that the soil only supplies the food- which enables the plant to draw from {jig, atmosphere those elemeuts requisite for it* physical construction.