Oh, no: it is only the rough, worn-out stuff. There is always bark left. It puts me in mind of _my_ hand, that got so horny after sawing a whole day at a big tree; for days after the rough skin got peeling off as if it was not wanted. Then you have more skins than one. You are just like a tree, for that has several coats to its bark. Which is the softer, the outer or inner bark? The outer is hard, and the inner soft. But there is a fresh gum tree just cut down: that will show us the barks.--Yes, now I peel off the outside, there is a very soft, juicy stuff, a thing I feel--a soft coat of bark close to the ring of white-looking wood. Mind, Willie, the outside is the _cuticle_ or _epidermis_, having pores or openings through which moisture issues at one time, and is absorbed at another. These _Stomates_ or openings are very small; in our Bush Pigfaces, that the Blacks eat, there are 70,000 Stomates to every square inch of skin. Then the tree perspires in the same manner that we do: that is odd. But what is the middle pulpy bark, with its green colour and sticky feeling? Botanists call that the _Chlorophyll_ or colouring matter. The inner bark is the _liber_, which you see to be soft and fibrous like, being full of sap. Why, this is something like our skin, as there is a watery stuff between our cuticle and the skin that has the blood in it. I have heard of people writing on bark: that must have been on the liber. It was so. The English wrote on the bok or bark, and thus we have the word _book_; while with _liber_ we connect the word _library_. But we shall return to the liber in another lesson. Is the cuticle always naked? No, some plants I have seen with hair over the skin, and others with something like scales. * * * * * Having talked of the bark, boy, we will turn to the stem. What are your notions about it? My eyes and fingers tell me that, after I pass the liber of the bark, I reach the fresh-looking white ring of wood, and that after that the wood which is still in rings gets harder and drier toward the centre. But I thought there was pith in the middle of a tree: how is it there is none seen here? Because these woody layers or rings have crushed it in time. I must say a little about this pith. You know it is soft enough; that is, because it is composed of small cells filled with juices at first, and then with air. Cells, father! what, like the bees’ honey-comb! Yes, indeed, and six-sided like those cells. The walls, however, are not made of wax, but of _cellular tissue_. This tissue is a fine membrane, or skin; or, rather, a transparent, colourless, film. Mucous threads connect the cells. What curious things to be in a tree? I shall astonish you more when I tell you that all your tree--root, bark, pith, wood, and leaf--every one of these is composed of a number of these little cells. Do you see those small spots in the wood, and these in this leaf in my hand? I do, father.