Laboratory work 4
The aim of the fourth laboratory is to see the directions of evolution of plant divisions in specimens. A herbarium or living specimen of a moss, a fern, a horsetail, a pine (or spruce) and a flowering plant is taken. First the vegetative organs (root or rhizoid, stem, leaf) of each plant are identified, then the generative organs: the spore capsule on its stalk in moss, sori under the frond in fern, the spore cone in horsetail, the seed cone in pine, the flower and fruit in the flowering plant. Then the main aromorphosis of each division is written down (stem and leaf in moss, conducting tissue and roots in fern, the seed in gymnosperms, the flower, fruit and double fertilisation in the flowering plant). Finally an idioadaptation is found for each species: pine needles reduce water loss, the grape holds on with tendrils, water ferns have floating leaves. Conclusion: aromorphoses produce new divisions, idioadaptations produce species.
Specimens: herbarium sheets or garden plants. With a hand lens view the underside of a leaf and count stomata or sori in a 1 mm² area (paper with a square hole). Safety: do not pick plants (use herbarium); do not touch poisonous plants; wash hands afterwards.