How a small intestinal roundworm contributed to genetics

Cross-sections at the right place in the uterus of a female Ascaris megalocephala can be used to locate eggs in different stages of the first segmentation mitosis*.

After fixation and coloration of the sections, the chromosomes appear colored. The egg of this parasitic nematode can then serve as a support for studying the chromosomal phenomena that characterize the mitosis.

The grainy taste of pear flesh

Sclerenchyma cells are derived from parenchymal cells, which form secondary thickening edges in the cell wall. These are rich in lignin, which practically does not allow any substances getting through, which finally leads to dying of the cell content. Sclerenchyma is thus usually a dead support tissue, whose task is mainly to provide support an mechanical strength. Depending on the shape of the cells, stone cells (sclereids) and sclerenchyma fibers are distinguished.