ABSTRACT
The phenomena of chemistry in particular, are of primary importance, because except the people know the constitution of the air, the water, and the inorganic matters that plants absorb, the people can never know the nature of their food or of the changes that take place when they pass into the substance of plants; and so it is with heat, light, electricity, with attraction, repulsion, gravity, with endosmose, with capillary action – these are all physical phenomena explored in very recent years, and conversance with which is necessary before any progress can be made in physiological botany proper, especially in respect of those processes that are concerned in the growth of the plant. Knight published at the commencement of the present century a series of papers, one of the most important of which was the experiment proving that the downward direction of roots was due to gravity.
