The presence, however, of apparatus or observers upsets the conditions, while above uneven ground or near a tree or a building the equipotential surfaces cease to be horizontal.
Cells treated by reagents, has been interpreted by many observers as a network of threads embedded in a homogeneous ground-substance.
In Spirogyra the pyrenoids are distinctly connected by cytoplasmic strands to the central mass of cytoplasm, which surrounds the nucleus, and according to some observers, they increase exclusively by division, followed by a splitting of the cytoplasmic strands.
Many observers hold the view that the chromosomes are pulled apart by the contraction of the fibres to which they are attached.
Rosenberg (1909) adduces evidence fox the existence of chromosomes or prochromosomes in resting nuclei in a large number of plants, but most observers consider that the chromosomes during the resting stage become completely resolved into a nuclear network in which no trace of the original chromosomes can be seen.