28. Q. What concentrations of living matter are there within a cell? A. A concentration called a _nucleus_, and sometimes a still further concentration within the nucleus, called _nucleolus_, or little nucleus. 29. Q. Of what substance is the cell wall composed? A. A substance somewhat like starch, called cellulose. 30. Q. When it becomes solid how is it known? A. As woody tissue. 31. Q. How is common wood made up? A. Of a number of these cells arranged side by side. 32. Q. Of what shape may vegetable cells be? A. They may be globular, oval, conical, prismatic, cylindrical, branched, or of any other form. 33. Q. What are some of the varieties of formed material into which the bioplasm within the cell wall may be transformed? A. They may be solid, as coloring matter, starch, crystals, and resin; or fluid, as oil and gum, or solutions of sugar or tannin. 34. Q. What is the most important of these substances called? A. Chlorophyll, the source of the green color of plants. 35. Q. What other product of vegetable cells is even more widely distributed than chlorophyll? A. Starch. 36. Q. How do cells generate? A. By self-multiplication. 37. Q. What are the simplest forms of plant life? A. Those that consist of a single cell. 38. Q. In the higher classes of plants what is the character of the union of cells which forms tissues and organs? A. It is permanent. 39. Q. What are made by the union of cells into groups? A. The woody fibers of plants, and the cellular tissue which makes the softer, fleshy and pithy parts. 40. Q. What has observation shown as to the production of new cells in the highest plants? A. That they are not produced everywhere uniformly, but in particular spots. 41. Q. What terms have been applied to places of this kind? A. Growing-point, and growing or formative layer. 42. Q. Where may growing-points and formative layers be seen? A. Growing-points may be seen in the tips of buds, and formative layers between the wood and bark of trees. 43. Q. What names have been given to the tissue which is here formed by the division and union of cells? A. Formative or generating tissue. 44. Q. What are in direct contrast to the generation tissues? A. The healing tissues, or cork tissues. 45. Q. How are vessels made? A. By the union of several cells, the partition-walls disappearing, while the union continues at the margin. 46. Q. What are bast-tubes or bast-fibers? A. They are long, pointed, thick-walled tubes, commonly united into bundles. 47. Q. To what part of the flower is the term nectaries, or honey-glands, given? A. To any part of a flower which secretes honey or sugary fluids. 48. Q. What is the first independent tissue formed in flowering plants by the union of cells? A. The epidermis or skin. 49. Q. What is each of the pores found among the epidermic cells called? A. A stoma, or mouth. 50. Q. What are hairs? A. They are epidermal structures, composed of one or more cells.